Sooner, I've definitely been in your wife's brain! In particular since becoming a mother, I feel like I fail everyone. I think you're on the right track trying to let her know how wonderful you think she is. Someone who feels reasonably good about herself can usually be a more giving person, wanting to spread the good feelings around. Maybe it seems like it is hard to convince her when you tell her directly. Let her overhear you tell someone how terrific she is. It seems like maybe your H really believes it if he tells someone else. She'll ultimately need a positive self-image which can stand without support, but knowing and really believing that you think she's wonderful can be an excellent boost until that happens. Knowing, now, that my husband really thinks I'm pretty special, even with all my flaws, makes me want to do all kinds of wonderful things for him.
Jeffo, I think I understand what you mean. It's about sex and yet it is about so much more. If my husband had sat back, crossed his arms and said, "So you want someone to listen to you. Well then talk. I'm listening." I doubt I would have felt very good about that conversation. Technically, I would have gotten what I asked for, but I wouldn't have gotten the sense of intimacy that I really wanted to come from talking. I think when your wife says, "So this is about you wanting more sex," it is similar to what could have happened with my conversation with my husband. So when she says that, your answer is "No. It isn't just about that."
Is there a chance all of this seems to be coming out of the blue to your wife? You've had this sense of dissatisfaction, attraction to another woman, and have found SSM (I hope I'm not getting you confused with someone else.) She hasn't. It all seems strange and sudden. She's wondering what's going on. Possible?