I would use whatever of the colors is her favorite and meander all over. Or check to see if there is a varigated thread with these colors.

I think it would be very pretty if you just do it all over. Your colors are great. Good contrast. Marvel

I love variegated thread.

I like the all over meander with the purple.

I always use variegated thread when there are a few colours then I don't have make a decision on one colour..lol

I might try the variegated, then you would see some of the stitching on the darker fabric.

maybe a bright or varigated yellow, to set off the stars, and contrast with the other colors?

Another idea is to do a FMQ design in each block - something like a set of circles or a flower design - might give it some dimension. I did this on the Think Outside the Block quilt I made and also an eight pointed star quilt I did for my dad - they came out pretty nice.

I am doing two rail fences right now. The center I have stippled and on the border of the first one I did butterflies using golden threads paper. Then I took the paper off and decorated the wings. Then I stippled around the butterflies.
Diane/Wyoming

Oh isn't that PRETTY!