Did you dry the quilt in the dryer? If so, the damage is most likely done. Hoping you didn't: Don't use bleach because then you'll have permanent bleached stripes where you now have pink. I'd try Oxyclean - it comes in a spray bottle. After that is washed out, I would wash it in Synthrapol. Good luck.
I always prewash flannel because it has a tendency to shrink.
Oops, didn't realize that you had already started the bleaching.