Love the blues - & I love hearts - if your sis is the kind that would like hearts, try them in one or all of the blue shades used in the blue blocks. Maybe all the different bright colors of hearts are distracting, but think it would blend together & have a whole different look w/shades of blue hearts.
Good luck in what you choose - BE SURE to send us a photo of your choice.
Have a blessed day & may all your quilts be filled w/love.