if her pain was constant in last 3 weeks,perhaps she need see doc,but I still think that's fine.
Clinically ,Sitting and bending pain mostly tell us ,the patient suffer from soft tissue injury not nerves damage.Anyway,see doc ,you are nothing lose.Take care.
I forgot to include this has been going on and off for 3 weeks. It bothers her most when sitting or bending.
if she have no problem urinating or moving heer bowels,you needn't too worry about,it will take time to recover.for adult ,they need six weeks to heal,young chirldren maybe less.
Of course,let your doc know.