Your wife is playing a very foolish and potentially costly game. The first time, I think I would have shrugged it off. She was drunk, people do daft things on holiday and it was only a kiss. I would have made it clear that I found it unexceptable and told her how it hurt and how disrespected you felt. But left it at that.
Fast forward ten-ish years and this time it's with a good friend in your home with your teenage children present. That's bad, Neil, that's really, really bad.
I think, and this is no reflection on you at all, she wants to be 'desired' again - to feel the thrill she felt in the first months and years of your life together. The romance, the passion and maybe she hoped to inspire jealousy. And that's the dangerous bit.
Alcohol strips people of their inhibitions, and the restraints we place upon ourselves.
Maybe when she's drunk (and all sense has left her) she thinks that by making you jealous, making you angry, she will feel your love for her as a women - rather than as the mother or the wife.
And this is why it is so foolish. By disrespecting you so profoundly in your home, in front of your friends and children, I think I wouldn't be able to forgive and I would never except 'I was pissed' as an excuse.
Are you happy, Neil? If not, it wasn't a good enough excuse and you have to decide where next to go. Do you want to leave? Would a seperation period help? Would counselling?