Time for a family sit-down. Tell the MIL and the AIL that the items were planted in the author's drawers for a purpose--to prove that the MIL is snooping. That the snooping was an extreme invasion of privacy, and the author wants to know why? The husband is no longer a little boy! (Kudos to him for standing up for his wife). Offer to go to couples therapy (MIL and author) to repair their relationship. Make it clear that the MIL is on the way to breaking up the family in ways she won't like and can never repair. Then buy the MIL some "cute" lingerie of her own. Then the author and hubby should leave the ball in the MIL's court and give themselves some distance from a toxic situation until MIL is willing to change.