P.A.
My daughter had this problem when she was little and i recognized it right away because i also suffered cronoc nosebleeds as a child and even up to my late teens, take her to see an ent. Ear nose and throat dr. She could be suffering from thin nasal membranes. If so then rolling over in bed could bump her nose and break one of the small membranes and cause bleeding. Being in the hot sun can also cause a gusher. I had my nose cauterized and the bleeding stopped. Thesame with my daughter. It's a bit unpleasant and sometimes has to be repeated, but it is well worth it.