Why is Savannah eating diapers and how do we stop her?

Pretty sure this hasn’t been asked before! My daughter has twins, a boy and a girl. Savannah has taken to eating diapers. (Let me know when you’ve finished laughing and can read the rest of this!) Corrie has to be careful to keep the diapers out of her reach, even the used ones, or she’ll just mow down. I suggested giving her a wash cloth to chew on. She said she did, but Savannah just throws it aside and goes after the diaper bag.
Today she took the trash out. Was gone for about 10 seconds and when she got back her 8 year old son said, “Mom! I can’t get Savannah off Kale!” Yeah, she was chewing the side of his diaper, plus she’d gotten her hand in his diaper and had a death grip on his penis. He was not a happy camper.
What the hell are we supposed to do???