Leverage the 53,651 meme to your advantage: contact all the Web 2.0 startup sites (Techcrunch, GigaOm, Webware, etc.) and tell them that her service is a rip-off of your idea.
In fact, her ripping off his idea could end up being better publicity than he would've gotten anywhere else.
If the accusation is public knowledge, she'll have a difficult time raising a second round.
Also, there's a possibility those site editors simply avoid mentioning her site at all, which would be just as good for the O.P.