I'd have thought the appearance of the residents, and your estimation of the honesty of the staff when you ask questions.
In asking this question I'm not in any way criticising your choice, but, if I may...why? Wouldn't it be better, and not much more expensive, to hire in help for her at home? As I say, this question isn't a veiled form of criticism, but, rather, motivated by the knowledge that before long I'll be facing a similar kind of predicament.