Hannie Caulder (1971)

With the Mexican Federal Police hot on their trail after a botched bank robbery, the Clemens Brothers, the vicious gang of brutal outlaws, Emmett, Rufus, and Frank, find refuge in Jim and Hannie Caulder's remote relay station. As one thing leads to another, before long, the defenceless frontier woman will find herself brutally attacked, stripped both of her earthly possessions and her dignity, and left for dead. However, a chance encounter with Thomas Luther Price, the most efficient bounty hunter in the American West, will pave the way for a reluctant alliance and Hannie's radical transformation from a weak housewife to a merciless gunslinger. Now, the untamed wildcat packs a custom-made, widow-making revolver, and she has made her list.

IMDb: https://www.imdb.com/title/tt0068675