She chatters at the birds and sometimes opens her mouth without making a sound. This is normal feline behavior. My cat can turn almost anything into a toy. Rings from milk jugs, rubber bands, pieces of tape, plastic and paper grocery bags, crumpled paper and cellophane wrapping. Most of these are safe.
Cats really enjoy playing with things that act erratically and are light and easy to bat around.
When my cats do this, I scratch the outside of the bag bottom and they swat the bag from the inside. This includes rubber bands. Although cats are much better than dogs about not swallowing small objects, cats will swallow strings or rubber bands - even with an object attached to the other end. Several questions involved holiday ornaments. Keep breakable or sharp ornaments above reach, also.