One of my fiancé's best friends is one of his female cousins. I'm fine with her being in the bridal party, but I know it would be more meaningful if she stood on the groom's side. I've heard it's been done before, but I've never been to a wedding where that's been the case. Does it look funny to have a member of the opposite sex on the bride or groom's side? I don't want it to be comical. Kylie, St. Paul, MN
Whenever a couple makes a decision to include a member of the opposite sex, the only factor that is truly important is that both of them are comfortable with including that person. If a man wants an ex-girlfriend standing with him at the altar, the bride may have reservations, and those reservations need to be respected. Likewise, if the bride wants her ex-boyfriend in her bridal party, the groom needs to be completely okay with it.
In your situation, it is a family member, and it sounds like your only concern is that it doesn't take away from the sacredness of the day. The best suggestion is that you alter the processional and recessional, so that there is less focus on any escorting the groomsmen would have been doing, as well as to not have the female attendant in a suit that matches the guys. Although it can be cute in some cases, the suit often lends a comedic tone and is distracting. Have her wear a simple and appropriate dress in the same color and level of formality as the groomsmen's suits.