Am I being oversensitive or is she just being mean?

Well there are some people who just feel the need to be better than everybody else. You can confront her about it and tell her to shut the hell up that's what i would do if she doesn't like what you saying she can always leave. Also i am just guessing here but i am assuming you are better than her in every way. Often whoever tries to make him self look better than the other is him self the worst of the two. But if she is a close friend i would still say CONFRONT her key word here is to not let her make you upset. You deserve friends that lift you up rather than bring you down.