I've just found out that my friend talks sh** about me with her boyfriend on a regular basis. She sometimes defends me or does stuff for me, but I found out that the other times she has been making fun of my insecurities with him, stirring the pot and making fun of the way I dress. He used to make snide comments when we were all together and hated me, and now I know it's because she was talking behind my back to him.
What should I do? Why would she even bother being my friend in the first place if this is what she really thinks of me?