That image sent a chill down my spine...
You should reconsider what rider/show style she uses if any.
She needs time off and full rehab.
After that, biking, Romanian dead lifts, leg press, and eventually squats, no lunges or yoga.
By doing weight lifting she should be able to reduce the tendency of hyper-mobility.
Also see "relaxin, joint injuries", and avoid high risk sports when levels peak each month.
That's no small injury and she needs to stop her previous behavior or she will end up will two trashed knees. No sport is worth that.
She can still fully recover, but if she continues to dislocates it she will never fully recover.
Sorry to say this, but she needs to stay away from riding those horses for at least 6 months, and perhaps longer.
One fall or bad dismount is all it will take.