@silverwizard that sounds like a horrible situation. I'm a little confused how she could be being harassed on FB if she's made her account Friends Only and then unfriended anyone who is nasty, though. You don't have to be wide open to the public, there (unless you are trying to run a business).
Locking her account down only addresses stopping that avenue for the harasser, though. It doesn't address getting the cops to handle threats. But is her harasser using multiple FB accounts?