Very sorry to hear this! My daughter had a similar injury (full displaced fracture of the humerus just above the elbow) due to a beam fall toward the end of her sojourn at L5. Here's our story. She had pins placed the day after the accident. Her arm was immobilized (but not casted) for three weeks. At the end of that time, the pins were removed surgically and she was in a sling as the healing continued. Our orthopedist believed in minimizing the time that the elbow was immobilized, as the longer it's locked up, the harder it is to regain full mobility in the joint.
As soon as the pins were out, she started PT for the joint. At first, bending it at all was very painful and difficult, but after a few months, she had regained almost the same degree of mobility as she had before the accident (her left elbow went about 10% to hyperextension and the injured right one got to around 7%). The bone healed perfectly.
The thing we were not expecting is that in the course of breaking the arm, she also incurred significant nerve damage. We first became aware of this after the swelling went down and she had a maddening tingling sensation going into her hand. Then she discovered that she could not move her thumb through her ring finger at all. We consulted with her doctor and were advised to wait and see what would happen. Fortunately, the nerve path regrew. Unfortunately, this can take a long time. The neuralgia she experienced from about a week out to about three weeks out was actually far worse for her than the pain from the break. She had to relearn how to move her whole hand -- her dominant one, of course -- and was in a hand brace for months to keep the tendons in her hand from shortening. She was in PT to recover hand mobility due to the nerve damage for far longer than for the bone break.
Her accident was in April. In November, she competed a L6 bars routine. Her right hand was fully functional, but she had no feeling in it at all, so she could not feel the bar when she caught it after her squat on. I'm still amazed that she was able to do it.
She still hates doing full turns on the beam on which she fell, but she never looked back from the accident and is now a L8 gymnast, a very good artist, and a modestly accomplished violinist.
Best wishes to your daughter. If they'll let her come in and do a little conditioning every practice, it will help a lot to keep her spirits up. Gymnasts don't thrive when they are cut off from all workouts! Plus the social support from teammates is critically important to stave off depression.