It reminds me of when I was in a hot tub at our local pool. I was with a friend. The hot tub water was really hot. After I had had enough I stood up and blacked out for a fraction of a second. I did not fall though and caught myself. I was in my 50's and that was about ten years ago. I suspect that the water was too hot. Never had a problem since. Hope this helps. Hope that it does not happen again to your daughter.
G.