She's going to cosplay as a human Mokona and she's asking us to design the cosplay for her to wear. There's not much to say. I kept it white and simple. Just added a few red details to match the gem in her forehead. The feet are normal boots, just extended to look like Mokona's feet. Thought about making them all plushie-like, but it wouldn't look good with the dress. So I kept it simple.
Mokona (c) CLAMP
Design by me
EDIT: Finally, I was able to scan this, so I uploaded for better quality.