When I get cramps in that kind of conditions it's almost always because I'm low in magnesium. Gatorade doesn't replace magnesium or calcium at all - did she have any other electrolyte replacement? It sounds like overuse definitely contributed.

I don't know that much about Atkins, but I would think that people who take it to mean eating a lot of meat would be functionally low in both calcium and magnesium, just because they would be getting so much phosphorus?

Just speculation and personal experience ...