I think you're heading in the right direction...just keep playing with it. Here's another thought: Label each fabric 1 through 7 and consider arranging in a diamond shape (an odd number of columns would look more balanced). Row 1: 1 2 3 4 3 2 1, Row 2: 7 1 2 3 2 1 7; Row 3: 6 7 1 2 1 7 6, etc.
You could also use your least amount of fabric squares at the corners or diamond points. OR lay them out diagonally: r1) 1 2 3 4 5 6 7, r2) 7 1 2 3 4 5 6, r3) 6 7 1 2 3 4 5 etc.
Have fun! Whatever you do, I'm sure she will love it.