Now I know why I don't have a sister -- I would have too much fun driving her crazy.
I have take classes from some pretty famous teachers, and they have been aghast at the way I work. One in particular was furious because I would not work in her color palette. She said her pattern could only look good in one color combination and she would not tolerate anyone using any other combination with her pattern. (I went to the shop owner, asked for my money back and left.)