First of, it's horrible that something like this actually happened.
Secondly, yeah she really doesn't have any good basis for her lawsuit. Sure one could think fault should be with this dating site because they are the ones that set the two up. But as it also says the man that assaulted her didn't have any criminal record, so there was no way of knowing he was mentally insane, and it is not like that is something you write in your profile when you try to get a date.
But sure enough just give her the right lawyer and a stupid jury, and she'll be laughing all the way to the bank.