First off, I am so very impressed by all of the thoughtful responses - they are a pleasure to read.
Second, it could very well be that she is NOT colorblind, but simply has bad taste (it does happen). She seems to be quilting "in the closet" like a Lone Ranger, not really asking for help, simply company, when she selects fabric. Also, her "going cheap" on supplies may be either a cultural or ingrained behavior based on a life long before or not concerning you.
How about this: buy a colorwash quilt kit - or other quilt kit that is particularly good for learning color value - and begin working on it yourself. Share with her AND SHOW HER what you're learning as you go - it'll be a sideways manner of teaching. Since you don't "do" scrap quilts, it'd also be a way for you to get outside of YOUR box for a good cause.
When I first started quilting, I took the Keepsake Quilting catalogue and used it like a technical manual - the fat quarter bundles they sell are coordinated (or solidscolors are gradated within the bundle), and I learned a lot about the skill of soft matching of patterns and colors.
Ask Keepsake Quilting to send her a free catalogue - when your next one comes in the mail, it'll be something to share, discuss ("I really liked this quilt/FQbundle because of [whatever] - what do you think?" "I really like the softness of this quilt -I don't usually like [whatever] but this really struck me") and slowly percolate between your chats. She'll be poring over the catalogue in her free time looking for ideas, and the visuals will imprint their own lessons.