Oh hun, it's such a pain when people are like this. Much like younger siblings antagonising older ones because they know if they snap the older one will get in trouble not them.
Please try to stay calm, hard as it may be. Deep breathing might help you not focus so much on what she's saying.
She doesn't sound like she's really being much of a friend to you though, and she certainly isn't helping you, do you have to hang around with/talk to her?
Keep being strong :-)
J x