Vinegar is your friend - an update on washing your fabrics

Well, it turns out that the lady whose fabric had bled in her white quilt HAD washed her fabric before using it!

She came over and together we took a fresh piece of the dark pink, wet it, put it in a white cloth and - Presto! - white became pink.

She bought this fabric at a quilt specialty store, and carefully washed it, dried it, and ironed it before using it. She'd used it in other quilts, too - colored ones though, not white backgrounds.

Well, I'd done some searching for ways to stop bleeding and ways to remove unwanted color, and all answers point to vinegar.
While she was here, we tried two different methods for removing color: one is a mixture of vinegar, detergent, and water; and the other is straight vinegar. Both had mild success. Then we tested a new bit of the dark pink - carefully put vinegar on a section that had not previously run (with Q-tips) until it was quite wet. After a few minutes I took a cloth wet with only water and smudged it around, and it did not bleed.

So, we've determined that I shall finish the quilting, then when it comes time, soak the entire quilt in pure vinegar, before finally washing it in water with some vinegar added to the wash.

And keep our fingers crossed!