Some folks have reported that a food change triggered a coat blow. I know my dogs don't always follow a schedule when they blow coat. Usually it's Spring and Fall but once in a while it's off season. Or one is prolonged or skipped. One shed might be very heavy, another very light. Not to denigrate more serious possiblities mentionned above.
Is it possible your girl is mixed with something like Lab? They have short sort of coats but they should also have a definite undercoat and man, when it sheds, it really blows. We, Lab here, have lots of shedding going on as we approach the start of summer.