How do I make this up with my best friend?

I'm Lisa and I'm 17 years old. My best friend Sarah and I crashed a guy's birthday party three weeks ago. Sarah is also 17 and after about half an hour some of the guys realised we were uninvited but decided to let us stay. They were mostly in their early 20's. We were both having a good time drinking lager and having a chat but also getting attention from some of the guys who were making comments and teasing us a bit.

Anyway later we were both still there but quite a few people had left and Sarah and I were getting more attention from these guys and although I don't know the exact number I estimate there were around 14 guys still there.

At some point Sarah had disappeared upstairs to go to the toilet and I was downstairs chatting to these two lads. By this point we both had had a few drinks and some of the guys were getting touchy feely with us. Sarah hadn't come down for a while and the two guys I was talking too just came onto me.

It was probably only around 10 seconds before the first one pushed himself inside me and I was being held on the floor at this point by around 4 lads. There being nothing I could do so I chose to go with it. I just did whatever they wanted including oral sex.

When the lads who were on me quietened down a bit I could hear a commotion coming from upstairs and I realised it was Sarah. I could hear several guys cheering and egging each other on but I could also hear Sarah crying.

Eventually after probably around an hour and a half they finished and kicked us out. Sarah was in quite a mess and wouldn't talk to me at first but eventually began screaming at me that it was my fault because I didn't stop the guys I was with and she could hear me moaning and the guys upstairs were saying I was giving blowjobs so they started making Sarah do this too.

Now she's not taking any of my calls or replying to messages and I'm just gutted. She's blaming me for what happened to her

How can I make her see I didn't want her getting hurt?

Lisa