J.C.
How about offering to make her an emergency kit? Needles and thread the color of her dress and the bridesmaids dresses. And any tioletries she might need (blotting tissues, make up, deodorant, bobby pins, etc.). You can go online to see what else goes into one.
You can also make up bathroom toiletry kids for the ladies room at the reception. Put it in a pretty basket.