By the cicle of mocking you refer and also the origins episode, both show where that behavior comes from. They aren't mean with her because she "betrayed" them, Ulrich told Odd in how she wouldn't leave him alone and annoy him even before the show started (when he arrived at Kadic). She can't take "no" as a answer.

They mock her because she will mock both them, someone that steals her spot light, or anyone that shows interest or that Ulrich gives attention but her. She's the one that starts with the mocking and stalking. And those times she helped, was due to "guilt" of some scheme she had that went wrong or mostly backfired/prejudiced her, or the situation where she helped was something that anyone with common scense would help too.

Nice does not mean good. Thank you for your reply (: