Should have kept it between the two of us, i regret so much now?

So i have a friend at school and one outside of school, the two of them used to be really good friends but they kind of drifted apart. So lately, the friend who is at my school now have been excluding me and I have been telling how I feel, and complaining to the friend out of school. I ask her not to tell the others and i trust her that she won't. And today, i hang out with the friend at school, and she told the friend outside of school. That friend got upset and said that i never want to catch up with her but i hang out with the others. She said I always complain to her about what the other girl did but never go out like friends any more. I told her that i thought she wouldn't have time unless it's in the holiday because she got really popular. And she haven't reply yet.
But now, I'm scared that because she's angry at me, she will tell the other girl what i have complained and all that. I'm scared that both of them will dislike me, one because she thinks that i'm not her friend, and the other because i talk about her to the other one. I know that i shouldn't have told the girl about the problems that happened between me and the other, but i was really upset and i just need someone to talk to. I regret deeply now and i don't know what to do.
help?