How to deal with this annoying girl? :/?

Well she's is a kind of hi-bye friend, im not trying to sound full of it but whenever I do something like, wear something nice, going to meet someone, talking to someone, do my make-up differently. She makes this weird face like when someone gives you the 'dirties'? then she puts her poit of iew down, which shouldn't but does really shattermy self confidence, if it was someone else i wouldn't bother but she has heard all sorts of rumours about which are DEFINETLY NOT TRUE they were spread by these girls who are like realll jealous of me because i was in a relationship with a guy and one of these 'jealous girls' liked him and she hated me for being with him so her friends hated me too. When me and him broke up they spread really dirty rumours about me, which she knows about because she is their friend. The way she looks at me just gives me the creeps, she gives me that look like 'i know something about you' and i can't do nothing but sit there with a confused face because those rumours are not truee, she critisizes me in soomany way infront of everyonee and the rest of our friends it shatters me, yes I sat down with her once told her everything about my past and she gave me sympathy, but whenever she critisizes me and says something about me i can't help it but to say something back and thats when she threatens me by saying 'do you want me to tell everyone what you done in the past?'

Could you please help me on how to deal with her?

To be honest i don't even want to know her anymore eventhough we have common friends!