What about Toph? I'd want her as a sister!

Toph for sure.

ty lees never ending happiness would freak me out though

LoL zanhar1!

or ty lee

big time Tai Lee kataras to bossy mabe Mai

First Toph, definatly, then Tai Lee.

i love them all i pick all of them itsep for azula

well not azula or Mai so either Katara ot Tai Lee but you cant date your sister so i choose Katara, Tai Lee is just to hot

Mai is bored of everything, Azula is insane, and while Ty Lee is cheerful and positive, she doesn't seem too bright to me.

Azula, because I could finally have someone of equal intelligence to talk to, even if she is evil. Although, Ty Lee would be a cool sister too, since she's so cheerful. I don't think I'd want Katara as a sister, she'd drive me nuts. Mai would be way, way too bored all the time.

All of them but Katara, AZula would be my favorite sis though shes amazeing.

I agree with the first thing Citation said. I'm not going to lie, I'm the smartest person in my year at school and I find it difficult to have a serious or even semi-serious conversation with anyone without it turning into something incredibly stupid.
I'd want her as a big sister though. I would look up to her because she is poweful and clever but would ignore the more evil side of her.

Definitely.