L.U.
Totally not trying to freak you out....
My friend's son had an injurty where he fell off of a scooter.
He hurt his knee, but nothing serious. It just never got better. Same thing you are talking about. No certain reason, it would just happen.
She finally took him to the doctor after about a month and he was diagnosed wtih Leukemia. He has been battling it for 3 years, just had his 3rd transplant.
If she is not getting better then she needs to be looked at.
L.