Two of my best friends share the same birthday (they don't know each other). Friend1 had planned for us to do trapeze and then a sleepover at hers, to which I agreed to. The now friend2 has arranged a sleepover for her birthday on the same day, even though she was well aware of my plans. My whole group of friends is going to friend2's sleepover and I already feel so left out. I know that they'll laugh and chat about it non-stop at school the following days. I really want to go to trapeze with friend1 and then sleep over at friend2's place. I feel terrible about ditching friend1 but I really don't want to miss out. What do I do in this situation, how do I tell friend1 without hurting her feelings? Please help.