There are repeats because she only used six layers of fabric, which produced six blocks!
You can use either 11 fabrics and have one block for each fabric that is in the quilt, or you can layer 12 fabrics and not every block will have every fabric! but you will have an even number of blocks for your quilt instead of an odd number!
The more fabrics you add the less pieces are going to be repeated, and if you use the same number of fabrics as you do blocks you won't have any repeats!