Sorry to hear this.
Most importantly, document *everything*. Take lots of pictures. Keep everything someplace she can't get at it (a friend's house, a safe deposit box, whatever).
You do need to find a way to get her evicted. The only things I can think of offhand are either to get the police involved (not sure if they can help, but maybe they can charge her with theft/larceny) or to document the condition of her room and bring in the landlord and the health inspector (particularly if there are vermin - if you do that, though, document the clean condition of the rest of the house so it's clear that it's just her).
Do you think she may become violent if confronted? If so, you'll want to talk to her in a public place - and in any case, it should be all of you, not just one of you.
Demand that her next (hopefully final) rent check be a cashier's check or money order, since she's known for writing bad checks.
I don't know if any of this helps, but I hope things work out. Take care.
