Grease

The reason why I don't like the stance that Sandy changes solely based upon Danny is that she's her own character and the film does a beautiful job of developing every character individually, and therefore that makes the couples and pairings that come together all the sweeter. Not to mention, Danny changes for Sandy, too. He literally earns a Letterman for Track, which he joined to change for her! And in You're the One That I Want, the whole point is that she's saying that he better shape up!! It's not even reading in between the lines, she says it right there! She didn't just change her style, it was clearly symbolism of her attitude towards her lifestyle and personal confidence, which amplified by the end of the film, and that doesn't equate to her morals or values changing.