Help! First seizure for 12yo daughter

I am bringing my 12yo daughter the doc tomorrow, but I’m worried, and would like to hear others' thoughts. My daughter has no history of any type of seizure activity. On Friday, she competed in a large cheer competition (lots of stress), then spent the day in the pool (lots of sun). She had a good dinner and drank a decent amount of fluid, so I don't think she could've had low blood sugar or have been dehydrated. The next morning, while I was braiding her hair, she asked for water just before stiffening and falling against my legs. She started rapidly blinking her eyes, smacking her lips, and shaking her arms and legs—all very rhythmically. She was non-responsive for the duration of the seizure. When she came to, about 60 seconds later, she said she heard what sounded like rice being poured in a glass bowl. She also told me she had asked for water (just before her seizure) because her abdomen felt very full, and she felt it was a little difficult to breathe. What could've caused a seizure? Surely stress and sun wouldn't? Also, it seems like she's too old to suddenly have epilepsy? What are your thoughts? Anyone have similar experiences?