Who to invite?

I just recently started high school. It has been going well and I have lots of new and supportive Christian friends. I've been going out a lot more to things like movies, parties, sleepovers, etc. I know I feel really hurt when I'm not invited but I still feel guilty about something. I had a sleepover with some of my closer friends and we met up with some guys at the movies too. One of my friends got a text from a girl who hasn't been doing so well lately socially asking her what she was doing over the weekend and we decided to lie and tell her my friend was going to her vacation home. Well, at the movie, the girl's sister saw us and told her and now the girl is really hurt. I want to blow it off like it's not a big deal but some of my friends lied to me too about an event they were going to and I wasn't and I am still kinda mad at them. My friend doesn't know what to do either now because she and that girl used to be pretty close and she never intended to hurt her. She is asking me for advice and I have noooo idea what to tell her. HELP!!!