At most she may have commited some kind of theft of service.
Seriously, you feel guilty if you pee in a public washroom without having to fork over money for something you don’t really need? I visit Mcdonald’s drive thru a couple times a week and if I ever have to go in to use the washroom because I’m far away from home, and I don’t “buy” anything on that particular visit then Oh well! BTW the workers maintain the bathroom as a regular duty, whether 10 people use it or 100.