My mom & I cleaned my grandmother's wedding dress in the bathtub so I could wear it - yes, it was 50+ years old, true satin, and dirty from years of storage. No commercial cleaners would touch it, even the "specialty" ones. It wasn't a pure white gown to begin with (more an eggshell) but we got tons of dust/dirt out, and no stains. It looked great! totally vintage.
Fill half the bathtub (or container you use) with lukewarm water and small amount of mild detergent, just enough to make a few suds. (The previous post suggests oxiclean - works great on my laundry, but I would make sure the oxiclean granules are totally dissolved in the water before putting the dress in!) Soak your dress and agitate by hand a few times. Drain tub & rinse in clear water... repeat if needed. Hang to dry.
Just a note, keep in mind that you (or your daughter) will eventually want to wash the finished quilt also sometimes. Great idea!!