Bloody hell group paranoia.Lol
It would depend upon the age of the girl, if she's over 16 it's her own decision anyway and there's not much you can do about it, where they were meeting, who she was with ( lone meetings are never a good idea), whether she'd had web cam chats or just text chats, whether they'd correpsonded for years or just for a few weeks, whether they had phoned each other and we had landline phone numbers, checkable adresses etc, there are lots of variables which all need careful consideration before a rational decision could be reached.
Just because it's the internet doesn't make it automatically dangerous and just because people meet face to face first doesn't make it automatically safe. My kids have met with a lot of people that they've met on the net and oddly enough none of them have turned out to be filthy old perverts, but that's because they are very careful about who they chat with,the types of chat they have, what they arrange and they very careful to safeguard themselves and so are we.
Take stock of who it's supposed to be etc, how safe the meeting will be and take it from there.