I tend to really like cowboy/western names for boys. [name]Do[/name] you think frilly names or more unisex/surnames type names go better for sisters?
I think frilly names go well but also names like [name]Bridget[/name] and [name]Georgia[/name]. To me, those are tough but really feminine. I don’t think a unisex or surnames would make her stand out from boys with strong, masculine names.
I think something kind of in the middle of frilly and unisex works with western/cowboy names. A name that’s not too girly, but still feminine and kind of spunky and playful, to me, is a cow-girlish name, so that’s the direction I’d go in. Some examples:
[name]Bethany[/name]
[name]Caroline[/name]
[name]Clara[/name]
[name]Lucy[/name]
[name]Megan[/name]
[name]Maxine[/name]
[name]Samantha[/name]
[name]Susannah[/name]
[name]Brooke[/name]
[name]Anna[/name]/[name]Annie[/name]
[name]Cassidy[/name]
[name]Jane[/name]
[name]Kimberly[/name]
[name]Hope[/name] that Helps!
I think [name]Scarlett[/name] would be a good fit. It is bold, a bit frilly, and a bit tough.
A couple more:
[name]Pearl[/name]
[name]June[/name]
[name]Viola[/name]
[name]Opal[/name]
[name]Cassidy[/name]
[name]Odette[/name]
[name]Ruby[/name]
Might be several ways to go with this.
Old-fashioned, Genuine:
[name]Kitty[/name]
[name]Nelly[/name]
[name]Josie[/name]
[name]Dinah[/name]
[name]Jemima[/name]
[name]Susannah[/name]
[name]Maisie[/name]
[name]Tabitha[/name]
Contemporary Western [name]Feel[/name]:
[name]Cassidy[/name]
[name]Avery[/name]
[name]Casey[/name]
[name]Callie[/name]
[name]Sawyer[/name] (I think it is fun for girl, but I might be alone.)
For some reason I think Irish surnames work well:
(But can’t think of examples.)
Western Place Names:
[name]Nevada[/name]
[name]Sierra[/name]
[name]Aspen[/name]
[name]Abilene[/name]
[name]Green[/name] Names:
[name]Brooke[/name]
[name]Prairie[/name]
[name]Dove[/name]
[name]Paloma[/name]
[name]Wren[/name]
[name]Meadow[/name]
[name]Sage[/name]
Genuine Native American: (But be careful.)
[name]Winona[/name]
[name]Tanis[/name]
Nizhoni
BUT SEE HERE FIRST: Native American Baby Names for English Speakers
From the names suggested, [name]Caroline[/name] and [name]Scarlett[/name] really popped out at me as being a great compromise between throwback, modern, frilly and tough!
Thanks for your thoughts, and I love [name]Scarlett[/name]! I like some of the less frilly names, but I like a lot of frilly ones, too. [name]Do[/name] you think something like [name]Marielle[/name] or [name]Aveline[/name] still works?
This is completely hypothetical, btw.
I so love hypothetical! 
I do think [name]Marielle[/name] and [name]Aveline[/name] work because you used to hear similiar names in the real [name]West[/name]. Perhaps it was because the people who settled the [name]West[/name] were independent, maybe because they were isolated from trends and community pressures. But I think those are the sort of name you used to hear in real Western towns just a generation or two back.