I hope it isn't anything serious. Other than taking her to a doctor asap to make sure it isn't anything life threatening, when she gets dizzy like that, try giving her a candy with sugar (not that artificial stuff). I get a little hypoglycemic now and then and just simply sticking a candy in my mouth - sometimes under my tongue coz I think maybe it works faster - helps. Could also be a panic attack
. They can happen even though you aren't stressed or at times you don't even think you're anxious about anything.