I crept in, and I was very disappointed that I couldn't pickpocket/sleight-of-hand the masks off them one at a time from stealth. Even if our own characters are hag-pawned by a mask, they can still be removed easily, and the effect itself specifically calls out removing the masks as an option for freeing the victim. Knocking them out and removing the masks before confronting Ethel, or stealthily slighting the masks from them by surprise before you face her, should both be options we can pursue in this encounter.
