It depends whose name is on the lease.
Not really, the landlord doesn't care which one of them is a deadbeat.
It would be just as stupid for her landlord to merely take her word that it was merely her room mate refusing to pay her share. You might as well argue that her room mate was the one who robbed the bank, and she just happened to be with her at the time. The cops would remiss not to charge her and let the system decide her guilt or innocence.
Its unfair but thats life
She couldn't kick that bum out and Craigslist another roommate?
Well that franking sucks.