Whenever the Handmaiden teaches you more fighting moves, you both remove the clothes or armor you are wearing. After you fight, she does not put her clothes back on herself. Instead of going to the Equip screen and reequipping her with her robes; put clothes on yourself and talk to her and tell her that she should put some clothes on. She will then put on her robes and when you check the inventory, you'll find you have more than one. This works every time you have the conversation with her. No one else can equip the robes, but they do bring in a couple thousand credits for each. They can also be broken down into components.