Responding to the talk about Megan Fox as Sarah Rainmaker, Lisa Charleyboy of the Urban Native Girl Stuff blog ponders who should play the role. Her suggestions are Q'orianka Kilcher, Melanie McLaren (Tkaronto), and Crystle Lightning.
I don't know much about Lightning or anything about McLaren, but these choices might be okay. But I'd still suggest someone 1) from the Apache or a related tribe, 2) who doesn't look like a Hollywood starlet, and 3) who can play a lesbian convincingly.
For more on Sarah Rainmaker, see Top Five Native Heroes and Rainmaker the Environmentalist.