sauce for the goose is sauce for the gander, what's

What applies to one applies to both, especially to both male and female. For example, After her husband went off with his fishing buddies for a week, she decided to take a vacation without him—what's sauce for the goose, you know. This proverbial expression, often shortened as in the example, was cited and described as “a woman's proverb” in John Ray's English Proverbs (1678).