Sarcastic Friends vs. Sensitive empathetic Friend?

Hi, I'm the sensitive empathetic friend. My sarcastic friends like to joke around and say hurtful things to me(assuming that i know that they are kidding with me). Being that I don't like confrontation nor hurting anyone else's feelings i usually laugh it off and take things in. But im sick of it, the last straw was pulled last night. We were out having fun and one of my friends made a comment, I thought she was being hurtful, i said "i hope you notice no one laughed at that one", she then repeats what she said to show that she wasn't being hurtful, i told her i was sorry and thought he was trying to be mean n she said "yea because you were too busy being a b!$#*". She just said it without any emotion, it was just like she was out to hurt me like she though i was hurting her. My thing is im horrible about comebacks and defending myself verbally. I cant stop being her friend because I need them to come to my birthday party but im so sick of being bullied and not say anything back. I feel powerless and not respected and its making my self esteem get lower.