J.W.
If she is actually passing out, then I would be really worried, but to be honest, it doesn't sound like she's got a mild concusion. It sounds like she's a breath holder. My friend's son did this, and it is a little scary. You can kinda see it soming though. Next time you see her about to pass out or looking dizzy, try blowing in her face to make her take a breath (that's what the doctor told my friend to do). It worked for him. Under all circumstances though, talk to you ped!!!