[ At first, he assumes that she means she's capable of enjoying being awful, which makes him want to sigh and tell her to stop trying to impress upon him the idea that she's so dark.
Then, he realises she's talking about sex. He raises an eyebrow. ]
I dunno, do you want to be my girlfriend?
[ He knows for a fact that she doesn't, which is why he can ask so easily. She'd already told explained to him the unlikelihood of her entering a relationship, and he hasn't forgotten, nor is he interested in changing her mind. It's just a way to answer her question while explaining his opinion on the matter: even if he found her attractive, he's not interested in casual sex. ]
no subject
Then, he realises she's talking about sex. He raises an eyebrow. ]
I dunno, do you want to be my girlfriend?
[ He knows for a fact that she doesn't, which is why he can ask so easily. She'd already told explained to him the unlikelihood of her entering a relationship, and he hasn't forgotten, nor is he interested in changing her mind. It's just a way to answer her question while explaining his opinion on the matter: even if he found her attractive, he's not interested in casual sex. ]