That is not what I got from the charging documents, I think what happened is that she got herself into a situation that was too much for her to handle.
The one thing that has been bothering me about this story is why these kids were so virulent in their behaviour, when it struck me this afternoon. There has to be a backstory to all of this, one we are not as yet hearing about. Reading the pdf charging documents it is clear that this was all about sex and teenage relationships.
I think what was happening is that Phoebe was using sex as a tool in her attempts to form relationships with the boys she wanted. Two of these boys have been charged with stat rape, so there were at least two, possibly others we don't know about, who had sex with her. It seems these boys allready had girlfriends, and for those girls Phoebe must have been very threatening. She was better looking than them and apparently willing to have sex, something that they perhaps were more conservative about. So how would they be able to compete with her?
One way to compete would be to become more promiscous themselves, but that would be risky since they were less attractive and stood the risk of damaging their reputations if they did, which might have all sorts of unpredictable negative consequences. The other way was the anti-competition method of turning their rivals romantic weapons into liabilities, which is what they seem to have done.
Basically what they did was try to isolate her by very publicly putting her in the middle of the crosshairs by exposing her sexual behaviour. This would have the effect of alerting every other girl in the school that she was a potential threat to their romantic interests, as well as making her a romantic pariah for boys. For them, having sex with her would get them bragging rights, but any attempt to have a romantic relationship would expose them to derision as a pathetic loser for doing so. The end result would be that she would become the kid that few wanted to be around, which in turn would make her even more vulnerable for further targeting.
If you think about it, this is a very effective way for a girl to eliminate a romantic rival with little risk, and that particular story probably plays out thousands of times across the country in every school (and beyond). In most cases suicides don't result though.
In this particular fight Phoebe probably turned and ran very early on in the conflict since she was outnumbered, but the other girls (being immature and all) just kept on pursueing her even though the war was won. Btw, I think that this was very much a girl thing, the boys involved were likely going with the flow in order to stay in their girlfriends good graces. For Phoebe it became unbearable. She would have desparately wanted it to stop, but on the other hand if she pushed the authorities or her parents too much about it there was the risk of her own initial role in all of this coming out and that may have been too much to bear as well. So in the end she did the only thing she thought she could do to stop it.
I imagine the build-up a bit differently. Pretty, new to our country, somewhat exotic new girl in school is seen by boys as a fresh conquest that they want to pursue. They are either actively dating someone and choose to cheat on her -or- in an on-again, off-again relationship that is currently 'off'.
They flirt with her. She, being new, has no idea who they may or may not already be dating. She is flattered. She accepts their invitations & begins dating first one, then after breaking up with that one, another.
The boys pressure her into sex. Or, maybe she even willingly consents to sex (although, she is still underage).
The boys either actually wanted to be in a relationship with her or were just dating her to see if they could get her to have sex with them, so that they could have bragging rights.
Either way, after the relationships end, they go back to their original groups of friends with either hurt egos that they bolster by telling stories that make them feel better about the whole thing -or- bragging, callous stories about how they were 'the man'.
The insecure girls, instead of putting the responsibility of their own rocky, dishonest, game-like relationships with these boys on themselves and the boys, choose a scapegoat. Instead of thinking "these guys are losers who would cheat on me just for fun", they somehow disavow the boys of any personal responsibility in choosing to date someone else and decide to blame the girl that they dated. That assuages their insecurity, too - "It's not that I'm not a valued partner in a relationship, it's that the boys were magicked away somehow".
The boys egos soar as the girls fight to keep them. The girls insecurities are fed back by the boys enjoying the fights. The tagalong girl-friends, just as insecure, thrive on the positive attention they get from everyone when they join in.
Phoebe sits there wishing she had just turned down the offers for the dates in the first place & wonders if everyone in America is like this, if everyone in the world is like this at this age and beyond.
Well, that's the way I imagine it, anyway