Technically Nanoha doesn't fit the traditional "psycho moe" stereotype like Rena and these other girls, but she's probably seen this way primarily because of the way she reacts to threats and challenges. Sure she's sweet and kind and everyone's best friend... just make sure you don't ever give her a reason to have to fight you.
The yangire tag aliases to yandere now, if I'm not mistaken? (or at least, there was talk of that being done.) But yes, Rena is definitely a yangire as opposed to a yandere. Kaede is, from what I gathered, only yandere in the anime - she seems to stick more to yangire in the original VN. Judging from Comartemis' description, Nanoha seems more yangire as well...? (Feel free to correct me if I'm wrong on either count, I've never played/watched those two series.) Kotonoha is the only very clear case of yandere.
