UPDATE: This film comes out tomorrow in the UK under the name "Sweet Vengeance", and there are clips available. The topless scene mentioned below is well-lit. There is also a view of her breasts (mostly from the side), as she walks into the river.
January Jones has a topless scene in Sweetwater.
-From The Hollywood Reporter:
Although the film is nicely decked out and features some distinctive moments along the way -- Jackson deliberately scratching the pretentious Josiah’s imported fine wood dining table, a topless Sarah gunning down two bad boys while bathing in a river --
http://www.hollywoodreporter.com/movie/sweetwater/review/414455
From Mr. Skin: "Sweetwater stars January Jones as a steely beauty in the Wild West, and she gives up the breast look yet at her double barrels an hour and 10 minutes in. January has slipped a nip before in The Three Burials of Melquaides Estrada (2005), but this nude scene is a full on funbags shot in broad daylight."