The Hathor Legacy has a post and comment thread about female characters on TV that start off absolutely wonderful, but change their personalities after a point as they get romantically involved with a male character they wouldn't normally be with and you end up with a character you despise. Betacandy calls it the Kincaid Effect, after the Law and Order character.
Its probably something to do with a changing writing team and cast, which of course makes me think of how comic book character personalities change as the creative team changes. Often with the female characters, you get the Kincaid Effect where a once-likable female character is suddenly the embodiment of every feminine stereotype you hate and coupled with a male character she shouldn't look twice at.
I've seen this happen in comics. It seems a common thing in team books, and outside of team books it can be very, very abrupt. I think the Kincaid Effect happened to both Jade and Donna Troy when they got paired off with Kyle Rayner.
Funny how the opposite effect happened with Guy Gardner when he got paired off with Ice in JLI. You'd think Ice would have to be changed to get with him, but really it was Guy's personality that was altered to fit her. Resulting in a much more likable Guy Gardner. (I'd call that skill on Keith Giffen's part. He could probably make me like Jade or Donna.)
This bears some thought.