I have this condition. I don't always faint, but often feel like I'm going to. I have discovered that a trigger for me is when I'm not regular. I have to seriously watch my fiber intake to be regular. When I slack on the fiber, I get backed up and the fainting spells begin. I have actually fainted 4 times. Teach her to put her head between her legs or to lay flat on the floor with feet slightly raised when she feels a spell coming on. Different things can cause the vagal response for different people. My doctor also didn't seem concerned, but it is a very frightening experience. Best of luck to you and your daughter.
I would consider seeing a pediatric cardiologist. Passing out is NOT normal for any child.
Hypoglycemia can cause this to happen. If she is experiencing dizziness/vertigo, there are medications to treat this (which would be up to her physician to prescribe). There are also centers where one can go to treat balance disorders...so that may be an option as well. I know it seems alarming, as it should to any parent. Most children are jumping about and movement like this can set it off...just as standing up quickly from a seated position.
Maybe make notes (or have her do this) of what she is doing and when she has them...and present that to the doctor at the next visit so they will have more understanding about the severity and frequency of them.
I wish you the best of luck and hope all will be well with your daughter.