B.C.
Hey girl
my son's arm is broken now too, which he is 12 and its the 3rd timein 2 years we are experts, Let her wear short sleeves and find one coat to wear over it and she should get a shorter cast in 3 to 4 weeks so she doesnt get a stiff elbow so theres some hope, As far as bathing, you want heavy duty trash bags and duck tape, wrap it around the arm and duct tape it thoroughly.
good luck