I have a group of friends and we're all pretty close, some more than others. One of the girls is named Leah. I also have another group of friends who I recently became friends with. I'm not super close with them and don't intend to be because they're seniors. Some people think they're fake and y because they're popular, but I know they're nice people and it's not like I am getting really close with them.
Yesterday, one of the girls from the senior group, Jackie, was having a pool party. My friend Leah was invited, but not another girl who I was hanging out with. I knew before that only Leah and I were invited, but Leah told the other girl she could come too, without knowing she wasn't invited. When I asked Jackie if she could come, she said no. So Leah stayed back and I went to the party. The next morning they called me a ing for ditching her and they now know I'm not a true friend. Leah was also mad because her stuff was in my car and I took it with me. I didn't realize her keys were there too. So in the morning, I drove to my house and met them to give Leah her stuff.
They then procceeded to yell at me and gang up on me about all the things about me they didn't like. They said they thought I had changed. They think I'd ditch them in a heartbeat for these other girls and that I don't care about them. They think I am selfish and don't think about other people before I do anything. Leah said it was annoying that I'm "constantly" asking how I look, which I know is not true. I am insecure, but Leah called me the most conceited person ever. She knows I have depression and that I'm insecure but she thinks I am always asking how I look. She has depression too though. She just gets annoyed, she said, because so many people tell me I'm pretty and she doesn't get why I need to be insecure. So she thinks I'm conceited.
I was crying the whole time and they told me I didn't need to be crying. I just need to realize what I'm doing. I called the girl who wasn't originally invited and told her what I had done was wrong and I hope she would forgive me. She said she appreciated it and she'd talk to me later.
I don't want to lose these girls because I'm so close with Leah and them, and this kills me. I don't know what to do though. This makes me hate myself. I don't think I've changed, I just think I made some bad decisions but I think them all ganging up on me is wrong. They called me some really hurtful things.
What do I do now?

I think you should talk to Leah with out anyone else there... Just tell her that you messed up and just say that she really hurt your feelings and you didn't mean to make her feel bad...

I hope everything works out :)

I would tell her the truth... that you didn't go to the party because you wanted to become best friends with the people there, you were just looking to have fun. If you didn't know that Leah wasn't going to the party I would include that too. Also say that she didn't have to yell at you like that. Because she hasn't made any mistakes before? If she's a real friend, she'll be mad at first, but then take the time to understand why you went to the party in the first place and forgive you.
Good luck :)