Least fave female character and why.
I very, VERY nearly put Ginny Weasley, but then I remembered this bitch. Ginny is an honorable mention, though.
I understand the point of Cho. I think she was necessary and I liked the build up of her and Harry's relationship. The character herself, though, was a whiny and annoying bitch. Yes, she had a reason for being an emotional basketcase, but that doesn't make her any less annoying. Additonally, while it makes total sense for Harry's first crush to be on a pretty, nice girl, there's really not a whole lot of substance to Cho. Maybe we would have seen more awesomeness if she'd been in the books more, but she was always just sort of there. Besides being nice and pretty, the only good things she did were play Quidditch and join Dumbledore's Army. So many of JKR's characters are out of this world fabulous, and Cho just wasn't at all.
Interestingly, I dislike Ginny for almost the exact opposite reasons. I think the character herself is pretty cool, and personality wise she seems like a pretty good fit for Harry. However, I didn't like the way she was handled one bit. Unlike the build up we got with Cho, Harry's crush on Ginny came out of nowhere (chest monster, anyone?) and just seemed quite contrived. It also seemed like Ginny's whole purpose as a character was waiting around in the background for Harry (with occasional acts of awesomeness, I will admit), whereas other characters existed far more fully outside of their relationships. She is definitely the most Mary Sue-ish character in the HP world, imo.