Im unsure if thats the case because she certainly didnt seem that way in the flashback. Maybe her master was using her the way she is using others to become stronger or something.
I'd agree that she's changed a bit after her master left, but clearly even before her main focus was becoming powerful, studying etc. Probably even then she missed some schmu "to be a real witch". True power comes from the heart! ... or somesuch thing. ^^
Not really. The four panels we are shown of her before being left alone depicted her as extremely attached to her master, working hard to gain approval. Only after did she decide to go for power at any cost.