Lens Hood Envy
It took a little demonstrating with her lens to show her that the front part of her lens rotates when it focuses. That means that the hood does as well...and if she were to attach a petal-shaped hood to it there would be various degrees of vignetting and light cutoff as she focused the lens. It is only with the lenses that do not rotate that you can use the petal-shapes.
In the end she accepted the manufacturer's recommendation...but I can't help thinking she was disappointed that she didn't get to use the pretty one.