Am I Being Used Or Over-Emotional? Please help!!!?

Ok so I play the guitar. Stacy (this isn't her real name) whom I was friends with and Beth (isn't her real name either) started to hang out with me towards the time of talent show auditions. I've tried hanging out with them b4 but I felt like they left me out too much. We became best friends and did everything together! But then they got mad at my other friend, Jess (I'm just gonna change all these names) for a reason I thought was stupid. They started texted her mean things and sadly I got into it too. We acted like we where the victims but deep down inside I agreed with Jess. I felt guitly so I texted her that I was sorry and I felt pressured into being mean and stuff like that but Stacy and Beth would get mad every time I talked to her nicely. I still feel guilty! But we formed this musical group for this talent show. I had a blast practicing but I got aggravated when they yell at me if I don't sing/play guitar right. So we got some gigs after the talent show then auditioned for a tv show. After that they don't even talk to me. (Present Time) At basketball practice I asked a close friend their opinion on the situation and they said Beth and Stacy hang out all the time at a lot of places! Stacy won't even text me back! I don't know what to do! I want to quit this musical group but I feel like I'll just cause more drama! What do I do???