Pffft. I don't even know what to say aside from the idiocy of a lot of members of the human race and their attitude toward other people (and animals) never ceases to amaze me. And anger me. I mean, we all have made 'beginners mistakes' (and even long after being a 'beginner'), but when you're proven to be wrong you need to own it and fix it. I mean that as a general rule, but I mean it especially if it's jeopardizing the health of someone/something else! If someone tells me something I'm doing could be hazard to my pets, even if it's not proven.... I'm going to stop it.
She's either lying about what the vet said, or her vet is just as uneducated in rat care as the average person who has never owned one. There are so many things wrong with her argument. It clearly isn't going to get drilled into her skull.
Oh, and how to report someone on Fb?
When you go the their profile, on the left under the column with "Wall, Info, Photos", scroll past their friends list, and underneath there is a list that says: Suggest Friends, Unfriend (if you are friends), Share Profile, then finally "Report/Block this Person". The convenience! Blocking and reporting at the same time! :p
(I'm on FB right now, no I didn't have all that memorized haha ;] )