This idea isn't sewing or knitting but I just wrapped a bear in toilet paper as a mummy for my mom. It turned out really cute. Not to mention it was all made from stuff I had around the house.
If you(or she) really want to go with knitting you could knit the bear a cape pretty easily. It could be super kitty! Or a kitten sized poncho, head band, and long hair it could be a hippie. Or make little leg and wrist warmers and a head band - it could be a 80's workout kitty
Now I am thinking about knitting something for my bear for Halloween