She's only partially surprised Lauren reacts this way; he's getting further and further away from being the person who could be momentarily shaken before giving into what he wanted, which she was finding she liked. It meant he was getting comfortable, which made her feel... good? Special, maybe.

While she wasn't necessarily intending for things to take this kind of turn, she's not opposed to it, so she goes ahead with it. She lifts an arm to skim her hand along his jaw as they kiss, twisting at her middle a little to do so over her shoulder. She makes a soft, titillated sound when he sucks on her lip, and she deepens their kiss by answering in kind, stroking her tongue into his mouth. Gently, in an bow of her back more subtle than before, she arches against him again.