Personally, I think the yellow background on the pinwheel blocks may be what's off. As others have suggested, I would trim down the ballerina block about 1 1/2", then add a 1 1/2" darker pink fabric. I would also add more white and pink pinwheel blocks, I do like the multi-colored striped pinwheels. I would find a bright, colorful print fabric for the backing of the quilt. To me the ballerina is soft and delicate, so maybe it's the yellow and brighter colors that may see off. It's going to be an adorable quilt with that ballerina in the center block.