Fat Alice

My white cat, Alice, who's sitting on my lap as I type this, has started peeing. This is not spraying but full-on inappropriate urination. I can't figure it out. I've got one of those automatic litter boxes, so it's always clean. Maybe my roommate moving back in last week has her freaked out a bit. Of done a bit of research online and environmental stress can be a trigger for this type of behavior. Either way, I'm going to have to take her to the vet when I get some money. If it's not one thing, then it's the other. Any ideas?