If she isn't into it, it ain't happening. And what is worse is that she may wonder why you want her to do it. Like don't your love her? Or I am not going to be a slut...etc......this is a very touchy subject and needs a lot of sober communication. Or she may just write it off as you being in a drunken stupor and out of your mind.
Before my wife and I got into cuckolding (something I had wanted), when we were having sex I would tell my wife sexy stories that always involved another man. Maybe a guy in the bushes jacking off watching us or a threesome with a friend or co-worker I know she was fond of. It always got her juices going. Or we would read Penthouse Letters together which had a lot of great cuckolding stories and she always noticed how my cock would get hard as we read them. So it was an almost spontaneous thing when we had our first threesome with a good friend of ours as her mind was already in the cuckold world. Indeed, he stayed over that night in our marriage bed and they locked the door. I slept on the couch in agony as I listened to a lot of moans and grunts. She was hooked.