[Well, in a situation like this, there is really only one possible outcome - though in this state of mind, Aramis' mood will most likely not be dampened even by a slap. Which comes completely automatically from Constance at this point, not even thinking about it; after all, there's very little else to do when someone kisses you out of the blue, now is there?]
[She does have the grace to look slightly taken aback, both by the kiss and her own slap, though.]
You could just mention it, without the kissing part.