they can if there is medical need for it.
basically heavy irregular periods lots of cramping etc etc etc

any of this is reason enough.
if the GP has been her dr for years and knows her well then he prob would as he would see it as 1 a precaution. but 2 as a way of regulating her periods.
most drs use it now as a regulator of periods and control of PMS not purely as a contraceptive.

maybe that is why she is on it and maybe that woudl eb a better way of broaching the subject
i was 14 when i went on the pill and wasnt sexually active till much later