Tell her not to expect an instant recovery. The hand will be stiff and inflexible at first. She'll almost certainly have to do some physical therapy to regain full mobility. A good therapist will give her a laundry list of exercises, and if she's been going to the gym and doing conditioning, she can add these exercises into the mix. It may start out really frustrating for her, but it will get better quickly, and gymnasts are super motivated to comply with PT regimes.
Once she's been in a splint for a little while and starts to regain mobility, she might be able to start doing more things at the gym, but you should be sure to ask the doc what is OK and what is not. Ask specifically about weight-bearing -- that was the key threshold for my daughter when she was recovering from her broken arm.
Good luck as she goes back. Keep the ice and ibuprofen ready! (Though, while we were warned to expect this, my daughter ended up not having any pain.) Hopefully she didn't have any nerve damage -- that takes a LOT longer.