I just found out i am "best" friends with the most horrible person ever... waht do i do?

Me and my friend were just discussing (not in a bitchy way) some of the horrible things she has said about each other behind our backs. She thinks she is this gorgeous blonde and is always putting other people down ... she does this to my friends FACE (i dont know why she puts up with it) and apparently behind my back i am always being called a fat sh*t and if she was me she would starve herself (i dont even think im that fat...). That is only the begining and she is just always saying horrible stiff like that. she always makes reaallly racist comments which i HATE (for example me and my friend are both jewish yet she feels its ok to go on about how tight and money grabbing jews are... its ridiculous especially as if it was any one of us it would be HER). however the worst thing she did which just pushed me over the edge was that she has a friend who works at my doctors surgery and she got him to check up on my file juts for her enjoyment!! She consequently found out about this illness