I like the one without the hearts. It's beautiful and I'm sure your sister will love it :thumbup:

BTW: I keep meaning to ask you about the quilt in your avatar. It is stunning! If you don't mind sharing is there a name to the pattern that you used?

The only thing that bothers me about the hearts are the colors.I think the dark fabric in your blocks would be nice and call me crazy what about white hearts? anything to brake up the big white space.
I am not a good enough quilter so I am intimidated to fill a big space with color contrasting thread.

Option 1, without the hearts. Use Rose L.s suggestion to put feathered hearts stitched in white in the snowballs. For the quilting on the rest of it, I would use blue thread. (The color that is sold for repairing denim pants; it's neither light nor dark and I think would blend with both shades of the blue). Beautiful quilt, and I am sure we are all demanding pictures of it when it is finished. (Lucky Sister!)

The quilt in my avatar has no name, I modeled it after a photo I saw. To get the effect, the colored areas are 6 x 9 finished with black strips on two sides that are 1 1/2 x 9 finished. You end up with a block that is 9x 9 finished with black on two sides. Then you alternate the layout horizontal and vertical to get the affect.

Without the hearts, but quilting the hearts instead. I think a pretty feather heart pattern would be beautiful.

I like the first one, that is a lovely quilt, I think it's perfect!

Without! I like the crispness of the plain blue & white. Some interesting quilting on the white, with white thread would be attractive. (Not hearts.)

I think a pale blue thread would look good.

My vote is for the first one as well. It is beautiful - she will love it.