A plot device that usually is carried out through magic, the woman is guaranteed to stay at peak health at all times. Usually this involves becoming instantly fit and athletic, and getting radiant skin and a fresh look. Depending on the author's tastes, many other things can be considered "less than optimal health". Like skin blemishes, rashes, or even sagging boobs!
Since health declines with age, the Perfect Health bargain may lead to eternal youth, instant regeneration/healing and immortality.
Taken to even more extremes, anything that didn't develop optimally at puberty due to malnourishment or genetics could be retroactively fixed, resulting in a taller, more well-built (dare I say bustier?) woman with a great bone structure. So it borders
Increased Beauty.
Here's a story with some Perfect Health in the middle.
Seven Deadly Wishes 2
Got any more?