It was a good question, and deserves a direct answer; there are two aspects to that answer.  The second aspect is that I've had a terrible time finding a copy of it.  My local video store doesn't have one, and my personal video library is in such a shambles that I don't even know whether I own a copy.  It finally showed again on cable, so I managed to tape a somewhat edited version and view it again.  But the first aspect remains a bit problematic:  it is not at all clear that Peggy Sue Got Married is a time travel movie.

That's not terribly surprising; in a lot of ways this film is difficult to pigeonhole.  It appears perennially on Comedy Central, yet is in some ways a very sad story with very little humor, and that mostly incidental.  Exactly what happens to Peggy Sue is never made clear; and yet it doesn't matter.  It is a delightful fantasy, extremely well acted by Kathleen Turner, who manages to move from teenager to tired middle-aged woman before our eyes in some scenes--and supported by many then-unknown excellent actors, including Nicholas Cage (as husband Charlie), Jim Carrey (as a friend and member of the band), and Helen Hunt (as the daughter).  It isn't about traveling in time; rather, it asks a couple of very interesting questions, and offers answers.  If you had it to do all over again, what would you change?  And if you could go back into your past and see how you got where you are, would it change the way you regard your life?

For Peggy Sue, she changed much less than she thought she would; and in some ways, she may have made her life a bit better.  She tells us that originally she had to get married because she got pregnant; in the replay, she is intent on not getting married, but her husband fights tooth and nail to convince her that he loves her and wants to marry her.  This is likely to help them in the early years of their marriage, as neither of them will feel that either of them was trapped, but that they chose each other intelligently and purposefully.  He also chooses not to throw away years pursuing a singing career which would never bear fruit, turning instead to his father's appliance store which we know would ultimately provide his livelihood.  I suspect this saved them both a great deal of frustration and disappointment down the road.  She makes a point of encouraging the school's brilliant nerd to use his intellect to create many useful products which ultimately would make him wealthy and respected.  The one choice she makes which sticks out in my mind as probably a mistake is her decision to pursue a sexual encounter with the Kerouac-type poet.  I think she realizes this after the fact, so perhaps she learned from her mistake; but I'm inclined to think that it might have created other problems in her relationship with her husband in the future.  And in the aftermath of it all, she returns to find her husband worried about her, dearly wishing for her not to divorce him for his recent infidelity.

But I'm well ahead of myself already.  I haven't told you the story.  Peggy Sue has been married for about 25 years; she married her high school sweetheart right out of high school.  He's the son of the local version of Crazy Eddie, a discount appliance dealer, but sees himself as the next Dion, his friends as the new Belmonts.  (If I just lost you, they were one of the big do-wap singing groups which dominated pop music before the Beatles led the British Invasion of rock & roll bands to the top of the American charts.)  The music having led nowhere, he now appears in raucous television ads selling stereos and VCR's.  They've been married since then, and have a son (spoken of but never seen) and a daughter.  But recently he had an affair with a young co-worker, and has been thrown out of the house.  Peggy Sue is going to the Buchanan Class of 1960 Twenty-five year reunion alone.

She chooses to wear a dress which looks very like one she wore when in high school; she even worries whether she will be the only one to dress for the time (and she is).  But quickly the reunion moves into high gear, despite the unexpected appearance of the husband, as we meet her grown friends and gain glimpses of their lives.  The brilliant geek to whom none would speak is now worth billions, and cheered as King of the Reunion; and Peggy Sue is selected as Queen, for best displaying class spirit.  But as they wheel the cake toward the front of the room, she suddenly swoons and collapses.  The last things she sees are the anxious faces of her husband and her daughter.

She awakens from this twice--and that is part of the confusion.  The second time she awakens, she has been unconscious and near death in a hospital bed, her exhausted husband sitting up by her bedside hoping she will live.  But the first time she awakens, it is 1960, and she has passed out in the school, having just given blood.  She is quite understandably disoriented, and the nurse sends her home; even here, she is uncertain, and knocks on the door of the house in which she hasn't lived for 25 years but which she must have left on her way to school this morning.  We are treated to her nostalgia, as she sees her family with the older eyes of a woman who longs for the security of a simpler time instead of the younger vision of a child who thinks everything she wants is in the future; and we wonder, if we are old enough, about our own families, the grandparents we have lost, the parents to whom we are not so close as we would wish, the siblings we did not cherish so much when they were always there but now do not see nearly enough.

Over the next few days, she tries first to understand what has happened, and then to change her life to avoid the pain which in twenty-five years will be so bitter.  She talks to the school's brilliant nerd, telling him about the future of which he can only dream.  He eventually proposes to her, but she declines, so hurt that she will not think of marrying anyone.  She has a brief night of passion with the school's rebel poet, but turns down his invitation to travel with him to Utah where a girl has invited him to move in to her cabin with her.  She alternately tries to derail her boyfriend's music dreams and help him be ready for the revolution which is just over the horizon.

But the theme which rises to the top in all this is her effort to avoid marrying Charlie.  She's been badly hurt by the recent affair he will have in twenty-five years, and holds it against him a quarter of a century before it will happen.  She tries to push him away, to change her life into something which might work in the 80's but would be unthinkable in the 60's.  And he keeps coming back, telling her that she is the most important thing in his life and always will be.

Eventually, in what is an emotional crisis, she agrees to marry him.  He has given her a locket for her 18th birthday, one which she was still wearing at the reunion; but it contains two pictures which confuse her, for they look like the same two pictures she remembers, those of her son and daughter as infants, and cannot be.  They are instead her own baby picture next to Charlie's.  This brings on such a flood of emotion that it's difficult to know exactly what turned her around.  Perhaps she realized that there was much happiness in her life with Charlie despite the problems which would come, and she decided not to sacrifice the good things to avoid the bad.  Perhaps in seeing the faces of their children in their own faces, she realized that the things she missed about the future were inextricably entwined with the things she feared.  Perhaps she just realized that the eighteen year old Peggy Sue and her forty-three year old counterpart were both still very much in love with the charming singer who tried to win her heart and make her happy all those years.  Whatever it was, she gives up her resistance and chooses to marry him all over again, and to take the same path she took the first time.

Then it dissolves, and she wakes up again, this time in the hospital in 1985.  It seems that she has been here in this hospital bed for days.  All of her friends have sent flowers.  And so we have what seems a satisfying conclusion to the whole story:  she has been dreaming this whole time, and has not been to the past at all.  But there's a curve thrown into this:  among the flowers is a gift from the rebel poet, who has dedicated his book to her and that one starry night they shared (she wisely tells her husband that it couldn't be her, it must be some other Peggy Sue, since she hardly knew the guy).  So we are left wondering whether she has visited the past or not.  But we are not left wondering about the point of the movie.  She and Charlie are going to try to put their marriage back together, beginning with dinner on Sunday; if she could do it all again, she would do it the same, even knowing what she knows.

But we haven't begun to look at the temporal anomalies here.  How much damage has Peggy Sue done to the present, if in fact she went to the past?  In fact, she's probably done very little damage, and the loop will likely be self-sustaining.  If we have time travel at all, it's probably an N-jump.  Consider the facts.

Peggy Sue did not choose to travel back in time; it happened to her rather abruptly.  Her actions in the past will probably have a significant impact on her first few years of marriage, but given 25 years, but we have every reason to expect that she will arrive alone at that reunion despite her changes, and again be queen of the reunion.  She has not prevented her trip back.

It's not clear how much of being old the young Peggy Sue would remember.  One thing which bothered me about Quantum Leap was that eventually Sam Beckett would leap out of the life of the person he had replaced, and that person would leap back in to it, with little or no notion of what had happened while he was in the accelerator waiting room.  Peggy Sue has the same problem.  For a few days, the consciousness, memories, and awareness of her future self have been living her life for her, and making critical decisions--and suddenly that aspect of her character is gone, replaced presumably by the younger version.  How much of that time will she remember, and how will she remember it?  If she remembered it all, then it would change again; but perhaps she would remember little or none of it, or (think:  where was that younger consciousness while the older version was reliving those days?) maybe she will remember the original timeline.  After twenty-five years, her memory is spotty at best--if she had forgotten that her father bought an Edsel, she could easily have blurred many other details in her memory.  Even if the two consciousnesses shared that time together (not really suggested in the film), the departure of the older one could easily carry with it all of the memories it had brought with it, and the mind would have to reconstruct a history which made sense and didn't involve time travel.  All of which suggests that at the end of the C-D segment, the same Peggy Sue will make the same trip back to 1960 and do the same things, which, as we have seen, had little impact on her reality, apart from having a book dedicated to her.

Or perhaps she was right, and the book was dedicated to some other Peggy Sue.