Buffy just stared at Ambrose for a good half a minute at least, trying to wrap her mind around what he'd just said. Grounded? He was grounding her?
"Oh, I'm sorry," she finally said, her voice sounding even like the calm before the impending storm. "You're doing this grounding thing all wrong. See, you're supposed to send me to bed without my dinner while I think about what I did. Oh, and make sure I don't sneak back downstairs at night for some ice cream or something. I haven't been well-behaved enough to earn that sort of thing." Her voice started to raise in volume as she spoke until her it matched the infuriated look that burned in her eyes.
"You know what? Whatever. I'm done anyway. I'm not hungry." She turned on her heel and stormed up the stairs to her room, hoping her angry but compliant reaction to his demands would tell of how angry she was. She stopped however, mid stride to look back down. "I'm sorry, by the way. For asking. I know it wasn't my place." And with that, she continued her march until he would hear her door slam behind her.