If she's rolling over tacks and nails, maybe there is more than bad luck involved. How's her vision? Is she even looking at what she is riding over, or is she just going along as though she has steel-belted car tires? How about her lane position? Is she riding in the debris-zone near the gutter? Does she have adequate bike handling skills to avoid the hazards she does see? Oh, do you two ride together? The rear rider doesn't have much chance to see the debris and avoid it. All of these things can attract flats.

Then again, maybe she's just unlucky.