J.M.
the other posts are right on. It could also be that she's getting involved in what she's doing and not taking time to go.
I am sure the parents are very frustrated, but an accident is an accident and not necessarily intentional.
Maybe they could set a timer that every time it goes off, she has to get up and go to the bathroom. Whether she thinks she needs to or not.
Age 5 is when a lot of new things happen. Starting school, changing classes, a multitude of things. Maybe she's stressed out about something new. If they've ruled out any medical complications.
I had this issue around 1st grade and it was mostly due to the change in school setting. I had just changed from one school to another, and the former school had closed classrooms and the new on was open around a mulitpurpose area. And the restrooms were farther away. But I had to make time to go.