to make a successful quilt- especially a scrap one all you have to do is work with VALUES lights-mediums and darks-
color, hue and scale have nothing to do with a successful quilt except varying scale adds movement.
lots of very well known quilt designers work completely in 'grayscale' while designing so that color/scale does not interfer.
if your friend can sort her fabrics into lights mediums and darks she can make wonderful beautiful quilts. i've made wonderful log cabin quilts people love that have some pretty bizzare fabrics in them if you look at a specific fabric you may be surprised- but when you stand back and look they work very well.
some people (see) colors differently- instead of trying to teach her to see colors the way you do maybe you could help her learn to balance the values.
when i'm going to work on a new bargello quilt i choose my fabrics- lay them out with a couple inches of each showing in the order i think they will go in then i take a picture- load it on the computer and print it off in gray scale- it makes it easy to immediately see if something is out of place or does not look right.