luvstoquilt

Make a whole cloth..cream on one side and gray and white stripe on the back

gramquilter2

I made a string quilt using just whites and off whites. It is beautiful.

Fabric Galore

I like the idea of a whole cloth quilt and then use a variegated thread for the quilting in the soft colors she likes. I have the same problem with a grandson. I made him a baby quilt in trip-around-the world, a T shirt quilt when he was a teenager and he loves it but he does not like patterns in a quilt.

Lucky Patsy's

How about a tumbler quilt? You could use an elongated piece for a more modern look.

Silk

Great advices and lovely examples in this thread.

I like very much this low volume quilt from Mias Landliv blog (I saw her name in other thread and it reminded me about this beauty):

https://es.pinterest.com/pin/33495590956085493/

https://es.pinterest.com/pin/251638697903015808/

It's a very simple design, it's soft and charming... and I love-love-love the crochet border!

If she preferes something modern, maybe she likes this extreme low volume quilt (in fact, it's a no volume quilt) from Molli Sparkles:

https://huntersdesignstudio.files.wo...al_free_20.jpg

Good luck with the search