Bitchy friend and I don't know what to do? Any solutions?

I have a friend and she is driving me crazy. I've mentioned her in a question or 2 before. First of all she is really attention seeking, she was very thin for a long time, we all thought she had an eating disorder. Now she has started to gain weight and I'm pleased, but she keeps bringing it up most days saying "Have I gained weight?" so people say how thin she is. She implied to my bf I was cheating on him, not saying I was blameless because I had flirted with him, but I wasn't cheating with him and she shouldn't have mentioned him because me and bf were already fighting and it made things Worse! We all have to do what she wants, if we don't she throws a strop til she we do. She has started taking the later bus in the morning, so she is 15 mins late to meet us, but if someone else is late she always moans and says lets go without them. She always has a new bf and shows them off, & brags when she sleeps with them. She's big headed & is driving us all mad with the selfish way she acts.