All of you have really good points. I think it is because she doesn't have a goal or something to strive for. She's just there. I always think she's hiding what she's really thinking and feeling. Could be that she'd make a great villain at some point.
Oh and whoever said she could be replaced by Renet, yes please! I'd love that. Maybe Renet can accidentally send her off to another time in the future and take her place for half a season or so...
Y'know, eventually, once we meet Mona Lisa, and Karai is restored to normal, all the girlfriends could be together and have one episode to themselves. Can you imagine all of them trying to work together to save the guys? I am partly joking there.