I just wanted to commend you on your evident love and devotion for your wife. That is evident in your post. What is also evident is that the two of you were on board and in sync with being kind of "free" about having a threesome, which is fine. Many people do it. In fact, many people I know do it. I even have friends that are completely polyamorous whether it be 2 couples together or three people or whatever. However love works for you, or if you just want to dabble in sexual play [which is what this sounds like], I think that communication is the toughest thing.
In my honest opinion, I think that the intoxication factor was mistake number one. If this was something that you guys were all on board with and thinking about trying, then you all could/should have had a very open discussion outlinging the specific parameters of this relationship or experimentation. It sounds corny, but it's not. This is the only way it will work.
From this point, I would recommend that all three of you sit down and tell each other "Hey, we want to be friends, we were happy with the way things were going and we were just drinking and having fun> BUT so things don't get crazy and we don't have any misunderstandings or alterior motives, we need to talk. My wife is totally on board with this, and I feel like the luckiest amn in the world because you're both gorgeous women, however [adn you say this to both of them] my wife is the most important thing in the world and I will respect her wishes." Then, each of you discuss your boundaries. If everyone is in accordance- great. If not, end it- right then and there. ANd let your wife know ahead of time that you would end it- right then adn there and that she is all that matters. She will feel reassured. ANd stand by your convictions.
Apologize for what has happened and for not making sure that her needs were being met. Get her back in your life and really work at that first. She loves you, she's just hurting and unsure of her own boundaries right now. Tell her you understand that now. Tell her you'll never let it happen again and that if the two of you, in time, can become intimate with someone else again, you'll be more careful and very forthright about it. Tell her that you value her even entrusting the fun to happen in the first place. She'll warm up to it again over time. Once bitten....
But make sure you follow up with corrective measures- otherwise this just turns to baggage...and it will go no further. AND DON'T LET HER LIVE AWAY FROM YOU-GET HER BACK IN YOUR HOME AND LET HER KNOW HOW MUCH SHE MEANS TO YOU!!
Hmm.....sound like I have experience? E-mail me off-list if you two need some info. about alternative lifestyles and I can put you in touch with some information pages and people. Don't let go of this situation. Take the situation and get hold of what's happening.
Good luck- you can do this. ANd don't always do this when drinking either- bad things can happen that way.