this is an under appreciated subject. For me, when my wife was active, I found that my wife kissing another man was very exciting and erotic. It meant that she was surrendering to him, even if both were dressed and in public, he would have her if he wanted.
I remember one particular time when she was having sex with a man who she did not like (perhaps was repulsed by would be too much.). Long story about how that came about - she and he were sitting on a bed and he and I were talking. Apparently boring her because at one point she fell back on the bed, apparently relaxing. The man made some moves right in front of me like first caressing her leg. There was no response from Cathie so I assumed she'd fallen arelax. Then he pulled her skirt up, got between her legs, parted her panties and fed her pussy his cock. (I left out a lot) When he pushed her up on the bed while he was embedded in her, she finally opened her eyes and looked shocked. While she did not protest, she was not responding. He tried to kiss her mouth but she turned away, which as ridiculous as it sounds, gave me a sense of pride. Apparently my wife also felt kissing was a very intimate thing. She was accepting this man fucking her but no kissing.
Then I saw it: I noticed Cathie's legs open a little bit. Then I saw her hips rise to meet his thrusts. My God, she's beginning to enjoy it. then there was no question as he went for a kiss on the lips and she allowed it and returned the french kiss with passion, at the same time I saw her arms go around him while she opened her legs further and bending them at the knee -- opening herself completely to this man fucking her.
It was all set off with that kiss - that was the moment she gave herself to him.
Here are some pics but not of her and that long ago night.chris