do yoiu have any liners at home hun? maybe get her to wear a small liner so you can monitor how much she's bleeding. ask her when she notices it kwim?

if she has started with af, or the gp suspects it, they may do some hormone screening to check on what is happening. it might be good to prepare her that they may have to look downstairs as well - that could be very frightening for a seven year old

hope your mum can get a car to you