My rule is one MONTH of waking up dry absolutely no accidents before the child may go for naps without a pullup on. They can be in underwear during the day but a pullup goes on for naps till I say so. We change back to underwear after nap so one pullup lasts all week just worn for the two hours of naptime so not expensive but necessary.

Since she is done in a month I wouldn't even be worrying about potty training other than if she asks and let grandma work one on one with her.