Well...she wouldn't be thousands of years old, having been yanked out of a time warp.
Coming to Man's World, Donna'd be a teenager in a world, where her sister, Wonder Woman, is already a world-famous superheroine, ..and that changes a lot. Maybe, she grew up on Etta's family's Bar-L cattle ranch, with Mama Sugar, Papa Hard and brother Mint - can't get anymore American, than that! Growing up with the Candys would give both sisters a presently non-existent history, with Diana's BFF Etta. I think having Donna and Diana tied to Etta is rather organic, ..as with Bruce and Barbara, with Commissioner Gordon.
Bonus! If her family is African American or West Indian, it adds a little ethnic diversity to Donna's backstory. Very modern. Very American.
As for her present day backstory, I've made no secret that I want to see Donna become a small-town Wonder Woman. I imagine her turning her photography into a lifestyle blog, like Duchess Meghan's The Tig, and using art to revitalize some depressed, little American town, fallen on hard times. Could that town be Etta's Texas hometown? Hercules's Oregon town, Lexinor? Why not?