关于反义疑问句和书中的对话书中的一段对话A:But you used to be really quiet, didn'

关于反义疑问句和书中的对话
书中的一段对话
A:But you used to be really quiet, didn't you?
B: Yeah, I wasn't very outgoing
A: No,you weren't. But you were always friendly.
我的疑问是“No you weren't"是回答B的吗?到底该如何解释这句话呢?还是自问自答第一个句子?还有,no you weren't在这里是什么意思?是”是的“还是”不是“呢?顺便讲讲反义疑问句的答法就更好了