There have been some great posts about this. Try using the "search" feature above.
I would never wash an unquilted top in a machine. A bag does not provide much (if any) protection against the seams fraying. Best way to wash an unquilted top is to baste the top to a foundation fabric and soak by hand in the tub.
I would probably use
http://www.retroclean.com . Someone posted that it worked well even in the bathroom, without sunlight. I think that would be the safest product to use.
If there is bleeding, I would go ahead and quilt the blocks and then wash in Synthrapol. Synthrapol will suspend unset dye particles in water so they can be rinsed away. For bleeds that have already occurred, it can take several washings in Synthrapol to remove all of them. I would not use Synthrapol for the initial washing of the top because it requires hot water, which could cause the fabrics to shrink in different proportions.
Is she absolutely sure she has to wash the tops before quilting? If they smell, maybe she could mist them with something like Nok Out to get rid of the odor. Stains will come out just as well after quilting as before quilting. I would want to avoid washing the top if at all possible. It's impossible to predict whether there will be uneven shrinkage, bleeding, or fraying of seams (possibly the worst of the three).