Some great suggestions, the neutrals would be elegant/classic but, If you have your heart set on some color.. I'd first find out what color accents she usually leans towards, as in warms (autumn kinda colors or cools ( blues-violets etc)..I'd then chose a multitude of "muted" colors in the warms or cools that she prefers..
*If she prefers the warms= off white/cream background
*cools= white background
* or a combo of both
If she doesn't have a preference to warms or cools then I'd choose some basic Primary colors that are more "greyed" down/less bright, which would bring them more toward a neutral state..Which in turn would make them flow with whatever accents she chose in the future...
And If you don't wanna mess with any of this.. Show her some pictures of different color combos (maybe of art, so she doesn't know about the possible quilt) let her pic out what she'd prefer on her wall lol..Hope any of this helps (smile)