"Is it to much to expect her to own up to her behavior and apologize? "

Demanding an apology from your sister would not make it sincere and no one can cause another person to change. I am sure this situation causes you sadness - I know it would for me. It would feel like an immense loss for me.

Short of the two of you going to a mediator/counselor to hash this thing out, continuing to love your sister without being a doormat, modeling healthy behaviors like you have been doing, and keeping a little distance is probably all you can do and that is enough. When you are around her, find something positive to tell her about herself and mean it because no one is all bad.