We have a few kids like that in my program at school.

Usually if we bitch enough to one of the teachers or a counsler, they'll pull 'em aside and explain that they need to bathe, brush their teeth and wash their clothes.

BUT usually it's not just them being lazy..most of the time they're depressed or something is going on at home..so be sensitive.

other then that, just walk in and go "God damn, something stinks in here"
and smell your shirt, and maybe she'll smell herself and get a clue?