Unoriginal hat is done and given:
I did the old bait 'n switch when I gave it to her - she knows I'm making the house beret for her (she requested it, picked out the colors, and approved the yarn), and was expecting that to be her birthday gift. I had to explain what the colorway was (see "bonus matching accessories," below) but the color does look a bit different in the chunky yarn. We immediately marched upstairs and did a preliminary try-on with her scarf, and it matches well enough to wear them together.
So I'm counting that one a success. My Mom is the world's single best receiver of knit objects and other handcrafted gifts - she wore it for most of the day.