I feel you and she should consider the winds around Norman, OK when thinking of kilt material. Wool will be heavier and less likely to "reveal the secrets" when billowing in a gust. Other fabrics may look too similar to the uniforms of the "Tilted Kilt" employees.
These considerations are yours alone, but the wool Wallace blue may be easier to obtain than a "Fabrics-R-us" upholstery equivalent.