Buffy was ready. She had to be to be able to stand toe to toe with them or close to it. When the speed came into play, she had to move to react immediately to have any hope of countering it. Instinct had her throwing up her arm to block the blow. He'd get a taste of how strong she was from that alone, though the force of his own blow did knock her back a step. She'd have to strengthen her core and foundation if she wanted to stop that from happening again.
Taking advantage of the room, she launch a flying roundhouse at Ambrose's head, bridging the gap between them again.