There's the taste of blood in her mouth, and different blood in his, and Klaus knows too well the heat of the kill. He's feeling it as well, and he's not going to ask her to refrain, or do anything to bring her down from that high any sooner than absolutely necessary. He kisses her back with that very heat, that hunger that's only partly about the blood, and if you ask him, it is sweet, and it is nice.

He just has really messed up standards.