Floral Flutter Sleeve Midi Dress

I purchased this dress online for a Summer evening wedding I'm invited to in Paris. When it arrived I absolutely loved it, the color, pattern, fabric. I thought I had found my dress. I ordered my usual size of medium, but it was too large. I ordered a small, and was extremely disappointed that it was too small. For such a fancy, and expensive dress, I would expect numeric sizing. I know Nordstrom has a fantastic alterations shop, but the way the dress is constructed and lined, it seems too much trouble to have it altered, especially considering the delicate fabric. If the sizing had been different, I would have given the dress 5 stars.