It just takes time my friend. If you really want it to happen you have to be patient and let her warm up to the idea.
For example, mine took a VERY long time to really start acting on the idea regularly. She was okay with the drunken threesome first, and that was a rare day indeed at the time. Eventually one of her guy friends enticed her into going to see him alone, but again this took a very long time and they had been texting and flirting back and forth for weeks on end. The next step was her getting with this other very good friend of hers and she stayed with him at a hotel for a week.
Only recently has she acted on my suggestion of actually having a local boyfriend. All this took around two years to come to fruition, but it's worth the wait if it's what you really want. Hell, she even slept with him on the first date so again, take your time, be patient and eventually things just might work out for you.
You will have a lot more luck if you let your wife find the guys that sghe likes rather than the ones you want her to get with. I mean, if there is no attraction there can you blame her? Your wife looks good, so I don't blame your friend for wanting to get with her, but it's more important that she feels the same way or it will never happen.