He raises his hands to show her that he doesn't have a weapon. ... That's not entirely true, but summoning his baseball bat isn't exactly what people normally think of when they're imagining someone armed. "Look, I gave you five dollars, I'm not expecting services from that."

Casper waits a moment, before very slowly adding, "Besides. I'm not... interested in girls." He flinches slightly - it's not something he admits to most people out loud. But his dad isn't around, so... it should be fine. Right? And if she attacks him for it he can probably fight back.