When we get a pet, we are assuming a responsibility for its life, health, and well-being. Cats ask so little of us... getting fed a couple of times a day, a clean litterbox, some physical activity, and love.
Each of these things takes only a few minutes of our day's time, and yet there is no shortage of people who try to cut corners by never playing with their cats, and/or using automated litter boxes, and/or free-feeding dry kibble. I believe all of these things are a part of the same problem, which is the owner's detachment from the cat's needs.
Cats are independent creatures and don't need us all the time, but when it comes to feeding them and staying up to date on their health needs, it's very important to to be there and know what is happening. Some crucial signs of sickness will be missed if the person does not know how much their cats are eating (and likewise, if the person does not clean the litterbox to see what is happening in there). And overeating could lead to obesity which in turn leads to health problems.
Scheduled feedings are extremely important, and should be done unless the person is not home for very extended periods of time. However if this happens on a regular basis, a cat is probably not the best fit for such a person.
Good on you for seeing the problem before it gets worse. Now you just need to convince your spouse. I really don't like her attitude of favoring one cat over another. I know people might bond with one animal more than another, but to outright refuse something that would resolve an issue one cat is having because it will force the other to change its habits is too much favoritism. Regardless, though, this change would be better for BOTH cats. Try to let her know that.