How was she heating the enclosure?
Was there something connected to the heat source to regulate it?
Did the snake have mites?
Has she taken it to a vet?

If you really want to know, you can take the snake to a vet and have them determine what the death was caused by. (I can't remember what the word is for that, lol) I think you'll need to refrigerate the corpse if you decide to do that.