Problem with a disrespectful friend?

I went through the SAME thing with a similar friend. Luckily I was able to phase mine (I think we both knew it was time) out but it seems your friend is a little more persistent. Just tell her (over the phone, email or text if its easier for you) "look I really used to enjoy being your friend but now it seems like all you do is put me down and I don't think we have an equal friendship. I'm sorry but I don't think I can continue to be your friend anymore. I wish you the best" or something similar. Name specifics if you think this will help trigger a realization in her. Maybe she just needs tough love this way and she will apologize or maybe this will be the natural end of the friendship. Good luck!