HELP. Facebook group targeting my girlfriend: What do I do?

[Aaron]

ok so there is this group some girl made at my school and my girlfriend is 7 1/2 months pregnant and there are dozens of comments from people calling her all sorts of names and the person who made it wrote in the info that she should "go kill herself and her ugly baby" and that my daughter will "be fucked up" because my girlfriend does all these drugs. THAT IS NOT TRUE... and I have reported it twice and had friends do the same but nothing is happening and I really don't want my girlfriend to see it. Do I call the police??? I have no idea what to do... I told my mom and she doesn't know anything but she wants to call the police... should I call the police or is there a number for facebook or should I call the police anyway..... I want this girl to get in trouble....
We spend every waking moment together she does NOT do any drugs... she's a GOOD girl I don't know what these peoples problems are im so pissed.... =\