fractured Ulna Bone

My 12 y/o fell off of a skate board and fractured her ulna about 3 inches from her wrist.  Our Dr. put a mesh type cast on her forearm covering her hand (not above her elbow) and gave her 4 weeks before checking to see if it is healed.  We are at the 3 week point and just in the last day or so, she is complaining of pain when she tilts her hand back (as much as the cast allows). Does this indicate that the bone isn't healing and won't be ready to have the cast removed at the 4 week point?