((hugs)) So I feel and hear your concern. And I really hear that you love, respect, and honor her--but also that you have fear inside that the surgery has negatively impacted her/you in many ways.
But I think you need some facts in order to review your premise, because the basic premise is flawed by personal bias that is mediated by fear.
1. Diet and exercise do not work. Ever. They are temporary fixes in an unaltered body and fewer than 5% can maintain a 10% weight loss over 5 years time. Fewer than 5%. To give perspective, even WITH altering the gut and surgery, I've heard doctors speak of 5 year results of maintaining the full weight loss at less than 5%. They count success if someone maintains a 50% weight loss over that same time frame. So weight rebound is REAL. This surgery isn't really WLS. It's weight maintenance surgery because it DOES help improve the odds that you can lose substantial amounts of weight and at least keep 50% of it off over 5 years.
2. You are used to seeing your wife morbidly obese. You are. And now you see her thin-ness and fear that she is thin and guant. Gaunt happens. Especially if you are older. But, give it 1 year. The fat re-apportions itself and gaunt features will fill out and soften.
3. All weight loss comes with muscle loss. The end. We must do strength training to rebuild muscle and tone. Everyone must--especially if they want to maintain the losses.
4. Yeah...some women lose libido with weight loss, especially if you are peri-meno or menopausal. It sucks...but should be temporary.
5. Personality and moods change with extreme weight loss--it's a process and a journey and it takes a while for us to get our heads "right". The best thing you can do is be super supportive and compliment her on how she looks and reassure her that you think she's smokin' hot. Also, woo her. Don't just "Hey mama, let's get it on." Women want romance, and caresses that lead nowhere other than to be made to feel special--to tell her you enjoy being close to her. Try titillating her mind and senses rather than the end game. Try doing that kind of stuff and see if her libido changes!!!
6. I can assure you that we do NOT get to the Morbid Obesity Ball due to character flaws--due to lacking self-discipline. In order to get there most of us have exerted MASSIVE amounts of will power, time, energy, and committment to yo-yo our way through our broken metabolism and I would claim that we have more willpower than you will EVER (as a normie) be able to comprehend.
The End.