She's immature. She did all the stuff just because she couldn't accept Helga didn't want to back to her old house. CHILDISH!!!
Though I do feel bad for her, she has been through a lot but she needs to mature.
She is immature and quite naive, and that got her having an immature love for helga, she couldn't accept the rejection, cause i think in her head it was "why can't you love me" or "why can't you bring our family to a better light in society" or something like that, and she wanted her back so much that got obsessed with Helga, let's not forget those girls manipulating putting more fuel in her desillusion.
(I'm not really sure if all of it isthat way though ) (〜￣△￣)〜
I feel bad for Helliane, there was never a reason to make her a villain. She’s loved Helga from the beginning and always did her best given the situation ;-;