I can't believe what some of you are saying here.
The girl was left on her own, without parent supervision, are you going to blame a teenager for wanting to have fun, are you going to blame someone that young for being naive!? That's why teenagers have parents, because they can take responsibility.
You can't even blame the kid for this, she trusted the guys and wanted to have fun, she didn't realise that this possibility could have occurred from people she trusted. You're blaming her based on, "If she had been more responsible and not drunk, none of this would have happened, so she takes the blame for it a bit as well," when she is young and naive and just wanted to have some fun.
Every action has a reaction? You think a naive kid out to have some fun with some people she knows would actually go through all the possibilities as you're saying?
You people are stating all the things that women do wrong, and yes, I'd say those in their early 20s if they do these things must be well aware of the risks, but girls these days want to look beautiful and if society - in its different ways (such as media and advertisements) - portrays beauty as wearing such clothing, then is it the girl's fault as well?! Don't you realise this was naive and didn't know about all the things you're stating she should have done.
What kid wouldn't want to have fun with people she knows? It was not her fault. All the aspects that led to the rape were not her fault. It's the fault of the parents for not teaching her how she should protect herself and that she should be more responsible, it's the fault of the boys for raping her, it's the fault of society and especially media for making her feel she needs to do certain things to feel accepted.