A broken arm....less likely than other broken bones. I've taken care of children with broken arms who continued to not seek treatment for days or longer but just favored the arm and made parents question something wasnt right and they finally brought them in and it was broken. Swelling of the arm can cause compartment syndrome(loss of circulation to other parts like fingers) and lead to gangrene and infection possibly. My sister walked around with slight limb with a broken bone for 2 weeks and no signs of infection. Another friend the same went to school and never did go to a physician. As a pediatric nurse my gut instincts would say a child her age if she had a broken arm she would be extremely fussy thus leading to parental frustrations and anger and possibly more injuries. Now if the fracture was an open one thru the skin- yes more likely for infection and death. But most arm fractures are not thru the skin. Most abuse cases in Evelyn's age we actually seen more femur(leg) fractures parents blamed on learning to walk and femur fractures can result in death quicker without treatment and the child would be in a great deal of pain. Also another common thing in her age is "nurses elbow" which is where the child is pulled up or dropped down by the arms and the bones in the elbow comes out of socket and actually looks and seems like it's broken but most times goes back in place with certain movements. My daughter had this and we thought her arm was broken just from her dad moving her from his shoulders via her arms. When they xrayed her arm it went back into place. Just a little insight into possibilities. Also a child her age truely does have alot of bruises due to learning to walk it's very difficult to determine abuse vs natural causes. Children bump their heads on coffee tables, fall off things when climbing, they lose their balance and land on toys. In her age you look for fingerprint bruises on the buttocks, face and arms.