"Oh...maybe that's just slang. Horse girls are girls that get really, really into riding. Or just horses in general. The kinda rich girls that have a horse bought with Daddy's money. And who do equestrian stuff as a sport. Get the idea now?"

She's not deriding those girls. She just wasn't one, and didn't have the wealth.

"And that's fair. It'll take some getting used to for me, if I gotta. And given that we're on King Arthur's home turf, I figure we will."