It seems from the history that your daughter is experiencing sudden blackouts in vision. Sudden blackouts of vision lasting for few seconds and recovering completely is seen in transient ischemic attack
. It is because of sudden decrease in the blood supply to brain.
The other common benign things to be considered are sudden change of posture, hypoglycemia
If the common reasons are not there, she needs to undergo evaluation by neurologist
as told by your ophthalmologist. Usually in the younger age group like your daughter no serious causes are seen. So no need to worry, but I still advice you to follow the instructions to rule out some rare causes as told by your ophthalmologist.