Answer- absolutely not! Your butterfly is a wonderful addition and makes your block unique. I don't think any of my blocks look exactly like the ones in the book but I like them. I second guess myself all the time about it but I've decided this is my quilt and I'll make it like I want it to be.
Your stitches are looking very uniform and hidden. It's coming along so well.
You didn't ask but I'm going to give you a suggestion just the same. It's very hard to know where to place those pieces once the lines you drew become covered up. For that reason, I have made plastic overlays for some blocks to help me keep everything lined up the way it should be lined up. I just use a large ziploc bag and trace the block with a fine sharpie permanent marker. If I pin the plastic over the backing fabric and line up the tracing I can slip the little applique piece under the plastic to position it and then fold the plastic back out of the way to stitch the piece onto my block. Sometimes I trace the applique pieces and sometimes I trace the lines on the backing. But, I don't trace on both. You can never line up both lines perfectly. Okay, I'm done.
Gorgeous block. Can't wait to see the next.