One of the things I love most about my wife is her exuberance. When has a revelation, a new way of thinking, she is all in. Every time. Without fail.
I think this situation is more complex than it seems. I think she believes J is on an emotional level that he may not be yet. I still think he thought it was a booty call. Obviously she knows him better than I do and I know it's folly to assume anything about anyone, but my solar plexus tells me he intended on cheating on his girlfriend and was taken completely by surprise when R made her honorable intentions known.
What happened after they parted is up for debate, but I have a feeling that he's in the doghouse for one reason or another. He seems to me to be the kind of person who, if left to his own devices, would be totally into seeing R with full knowledge of me being ok with it. I think he was dishonest with his gf and that was that. Now I think he has cut ties with R to salvage his relationship and family. And more power to him.
I do truly hope that they can re-reconnect after things smooth out on his end, but I also hope it happens with full disclosure for all parties involved.
Until then, we shall both wait for lightening to strike in the form of a unicorn, wood-nymph, satyr, cyclops or an honest politician.
Concern yourself less with love and more with loving.