Tell your daughter to have the quilt dry-cleaned. It will come out better, and stay clean longer if it's not crammed into a washing machine where all parts of the quilt can't possible be saturated with the soap solution, nor can it be properly rinsed to get the soap out so it doesn't attract dust and dirt to the quilt.
I take my quilts to the local laundromat where they have some extra large machines, and wash them on gentle with a bit of a soak system planned in. Then I rinse twice: first time with vinegar, to get the soap out, and the second time with plain water. NO fabric softener, as it attracts dust and dirt. The vinegar works as a fabric softener anyway.