A skate betty is slang for a girl or young woman associated with skateboarding culture. The meaning varies slightly by source, but the core idea is consistent:
A skater girl who’s attractive and laid‑back, often riding or hanging around skaters
Sometimes used more negatively to mean a girl who hangs around skateboarders without skating herself
The term “Betty” originally meant an attractive young woman in 1980s surf and skate slang, later evolving into “skate betty” for girls at skateparks