Definitely keep a watch on the string/yarn she's around. Friends had a kitty who chewed on thread and ended up impaling the needle in his mouth. She took the cat to the vet because it wasn't eating -- your mouth would hurt too if you had a needle in it!

I crochet and Kuhio used to try to eat bits of yarn. Once, I did not do a good job of cleaning up after myself and she ate a long piece. We noticed her having problems in the litter box. She had a piece of string sticking out of her. I had to get some paper towels and veeerrrrrry slowly, verrrrrry gentle pull the yarn through. We were very lucky that we did not hurt her because we've heard that this is very dangerous because pulling too quickly could cut the intestines.

Please be careful of the string/thread/yarn around. I'm not sure about bits of fluff. I haven't noticed that being a problem with our kitties.