Well having a bathroom related emergency could sour someone's day - and this girl certainly seemed to not be having the best day. She didn't go here, so perhaps she had come to see a friend and had a fight. The promise of gossip (and the fact that she had nothing else to do ...) prompted Betsy to smile and move closer to the girl.
"Well. Let me show you the way, can be a bit of a maze here I'm afraid. Elizabeth by the way. My name I mean. I've seen you around at cross school events." In other words, she knew the other young girl wasn't a mutant.