I've never been to a country-western party before, but I wonder if a cute little black dress with black cowboy boots would work? Or do you think it will be more costumey than that? It sounds like a fun party!
How about a jean skirt, boots (cowboy would be best, but I can understand if you don't want to buy some that you will only wear once), a pearl snap or plaid ls shirt with a cami underneath, and a cowboy hat?
FP wore this to a party once and I think this would be perfect!
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"Despite all your best intentions, sometimes, fate wins anyway."
i bought some things from jcrew.com and this pic reminded me of your post...
it looks like maybe a cute higher-waisted black skirt with it. i love the belt, it gives it a girly-festive touch.
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"i tell you one lesson I learned
If you want to be something in life, You ain't gonna get it unless, You give a little bit of sacrifice, Oohh, sometimes before you smile you got to cry.." -The Roots