The Big Roommate blowup

A friend of a friend of W's was looking for a short term place to stay, and we had a room that wasn't being used, so we volunteered. It represented some easy cash for our bottom line, and could possibly even pay off our floor early. For a few months it was weird but great, she studied and worked all the time, was never here, and cleaned up after herself. It wasn't perfect, her boyfriend stayed here to much and lately she'd been slow on the rent. So January second rolls around and we still haven't seen any money. I ask her and she announces she's moving out possibly on the tenth. She apparently wasn't going to tell us and just leave without paying. W let her know she should fork over January's rent now or pack up, and when I got home today, she had done just that. No "thank you", No F**** you, no nothing, just keys left on the dresser in an empty room. Easy come easy go I guess.