It has to do with skin care, diet, and genetics. The first lady may eat a good organic diet, but she has not taken care of her skin and doesn't make any effort with her appearance.
The second lady is all glammed up and is probably wearing make-up, but she has obviously taken care of her skin. I don't know who she is, but even a cook who eats sauces, butter, and desserts, etc., but in moderation, will not harm her looks.
Most people don't protect their skin from the sun, and that's what causes the most damage, though diet has a lot of effect too. Being a little plump rather than thin helps to make the second lady more attractive at her age, imo.
French women, for example, have a high life expectancy, are generally not fat, and look pretty good in middle age. They eat butter, white bread, meat, and so on, but in moderation. They also eat a lot of fruits and veggies.
A healthy organic diet doesn't lead to looking old; it's taking care of your skin that counts. A diet that is not perfect doesn't lead to being beautiful: it has to do with skin care too and just making an effort. I don't think the first lady has made any effort with her looks.