Does not make sense
If the bully really had grown up into a much better person then why was she being antagonistic when blondie confronted her about it. With all the Queen singing and all. If she really was changed then she'd do as you expect a good person to do and be apologetic and say oh I was so dumb as a kid. It just does not ring true that we are meant to see her as an ok person in the end.
This film would have been much better if she had just been an out and out bad girl of the film. It would have made sense. They could have had a proper until now overlooked by him nice girl, perhaps a friend of blondies who he ends up with. The way it is now just seems like they had a change of script right at the end and none of it fits together.
And why the hell could they not give Weaver's character a better looking guy than that. It's not like he needed to be able to act for the part any decent looking guy of age would have done.