Does my daughter have to get the mandibular anterior repositioning appliance?

Typically this : Applies to an occlusal appliance for the treatment of snoring and mild to moderate osa - if she was diagnosed with a polysomnogram then yes or cpap. If you mean because she is retrognathic or micrognathic & you are inquiring about distraction osteogenesis to surgically correct this problem, then the advancement "appliance" is removed - then yes, this is a viable and beneficial treatment.

Yes, possibly: It depends, if she is still growing and has a small lower jaw or excessive overjet an anterior jaw repositioning appliance may help stimulate more mandibular growth. If she has sleep apnea, the appliance can help open the airway.