For what it's worth, I once leaned over a teeny tiny candle flame (thing tea light) and a very small strand of hair brushed it. The rest of my hair had been put up which may or may not have been a bad thing, anyway I lost a foot and a half of hair on one side of my head in less than 20 seconds, and if my sister hadn't thrown me on the floor and beaten it out I probably would have gotten some very serious burns.
This is with ZERO products in my hair as well. No hairspray, gel, nothing. I don't think the OP was overreacting in the least to defend herself. The lighter girl should have been punished as well instead of getting away with attacking another student.