[She may not even be (quite) the most emotionally confusing of Jack's kisses today, either, given the way he reacted to Spike, but this certainly means a hell of a lot more than most people's. He never used to put a lot of weight into kissing people, but they've got a lot of history now and there's the added influence of having been married, which felt like a hell of a lot more than the single day it actually was.
Conflicting with that is the knowledge that this can't go anywhere and that (thanks to that unexpected reminder from Spike) he doesn't want to hurt Ianto either.
He's still fairly good at living in the now, though, and the current now includes a young woman he has strong feelings about pulling him close and tangling her tongue with his. Impossible not to react to that. His one hand eases more firmly into her hair while his other arm comes tighter round her waist to support her bending backward enough for the increased pressure of his kiss. What the hell. He can enjoy the moment, can't he?]