Recently my cat (1 year old) started actively chewing and tearing soft, squishy things when nobody's home or when out of sight. She particularly enjoys socks (many pairs have been destroyed, she literally tears big holes in them. Clean or dirty - doesn't matter, she'll steal any kind of sock available) and different kinds of sponges.
She is well fed and has many toys laying around, some of which are soft and squishy balls made from similar material as sponges, but shows no interest in them.
What to do?