If she doesn't stop forgetting to do the litter trays?
3 cats, 3 litter trays. I do them every morning, and she is supposed to do them every night. She wants to take the cats with her when she has her own place, and it's not happening unless I can guarantee she will remember to take care of them properly.
If they have to eat in the same room as pissy, shitty litter trays, so ahould she if she can't remember to keep them clean.