[Eternal]

Well if the school just found out then of course they're all talking about it. But if you just wait a week or so, it won't be so new anymore and people will stop caring. So if you're waiting two weeks to "break up" with her, people will probably have forgotten it by then anyway.
But if you still want to pretend to end things, just tell people that you two felt you were better as friends. That's a pretty typical way for friends to break up when its early on, so nobody will really think twice about it.