I am starting to feel that I actually dislike my disabled sister.
That's a sad thing to say. Why would you not like your own sister, disabled or not?
I am ashamed of her, she is a bad example to people
Shame can be a powerful motivator, but it is no excuse for hating people like your sister that are disabled. Love your sister and include her into your life.
She is a witch and I can't control myself when I am insulted.
It sounds to me like she is going through some kind of goth or emo phase. She will probably grow out of it one day, but you should not feel insulted or treat her badly. It's just silly sibling fights that really don't hold any weight and she probably cares about you a lot.