Headaches, Pale And Clammy Child, Sweats Lot During Cheer Practice. Can This Be Due To Exhaustion?

My 9 year old daughter is a school cheerleader. She is physically fit, eats very healthy. And drinks lots of water. Her cheer practices are in a non air conditioned warehouse (miami, florida). I always take a thermos of cold water with us to practice to keep her hydrated. These last couple of practices, she s been complaining of headaches , and gets a little pail and clammy. She sits out the rest of practice. I know it cannot be dehydration , because she constantly drinks water. She does sweat alot during her practice. Can this be some type of heat exhaustion? the only symptoms she has is the headaches.