This is such a sad situation. The problem is "loose" dye that is not set. It is probably still loose, both in the original fabric and on the yellow pieces, so a color catcher is worth trying. And it may take more than one session.
It is not only batiks that bleed. This morning I did a Retayne treatment on some Debbie Mumm SSI fabric that has little candy corns on a dark background. On original testing, it blend an orange/brown color terribly. The Retayne has set the dye, and I now feel safe using it in a Project Linus Halloween quilt for the hospital's holiday party in the children' ward.
I hope your friend has some success on her wedding quilt.