ACL repairs are done using a tendon graft from either the patellar (knee) tendon or the hamstring tendon. Which choice is better is a topic of ongoing debate and the subject of many studies.
We do know the patellar tendon graft makes it difficult for the patient to kneel on that side. This could make a difference depending on your daughter's event(s). Patients who hop and land on one leg have a little more trouble when the patellar tendon graft is used. This may be something to consider for many gymnastic events.
Make sure the surgeon is aware of your daughter's plans to return to gymnastics. The type of surgery and rehab program may be based on her long-term goals to compete.