An orthopedic surgeon would really have to make that decision. The type of injury determines what treatment is best. Most elbow ligamentous injuries do require some kind of intervention. Early diagnosis and treatment can provide a good result. It's best not to wait-and-see with these kinds of injuries.
Sometimes, a rehab program of stretching and strengthening for the entire arm is needed. A physical therapist evaluates the athlete and prescribes and supervises such a program. When enough soft tissue healing has occurred, then sports-specific exercises are introduced. This type of program helps make sure the athlete can return to his or her prior level of participation without reinjury.
Postoperative bracing for the elbow protects the healing ligament while still allowing some range of motion. An adjustable hinged-brace may be used to set the motion allowed. As the athlete progresses through healing and recovery, the allowed motion can be increased.
Bracing a joint that doesn't need bracing can result in joint contractures (limited motion). Check with your team physician or coach about what's best for your daughter given her age and injury status.