Buffy wasn't too sure how to explain the mark to a child. For one thing, she didn't know if the girl was a Supernatural or a slave. She kind of hoped for the second option, mostly considering Supernatural parents might have the Supernatural urge to tell Ambrose that she'd been out. Regardless, she'd resolved to helping find Edith's home, and she wasn't going to back out and leave a child alone because she was too afraid to let Ambrose find out.
"Well, you know how there are the special people who run this town? I belong to one of them, a vampire, and he takes care of me." She swallowed hard, remembering her resolve to actually somewhat trust Ambrose to do that. "This is just to let everyone else know that I'm taken care of so they don't worry."