My 7 month old always chews a comforter to get to sleep in her cot. It's a cloth which is about 20cm square which came with the leapfrog dog that sings lullabies, if she doesn't have that then in her pram she chews a blanket or muslin. She's been doing this for the last two months.
From reading another post I've just had a thought, is this dangerous as a choking tool for her?