My fiancé's sister is going to be a groomswoman in our wedding. She already selected her dress from Azazie, but now her wife wants to wear one of the sample dresses that his sister tried on. This wouldn't be such a problem, but she wants to wear it in the same exact color as his sister and bridesmaids because she wants to match his sister. My fiancé and I don't like this idea because we don't want her to look like a bridesmaid or groomswoman since she isn't part of the bridal party. Normally, I know I shouldn't be telling a guest how to dress, but in this case I feel like I should be able to tell her we don't want her in the exact same color. Any advice?