This Achievement is for giving Rosabeth of Melfia a change of clothes. She's the person who was turned to stone near Majula, the one stuck the switch near the knight with the really big sword. You can restore her to life by using a Fragrant Branch of Yore. One can be found just after defeating the boss in Sinner's Rise, the other is in Black Gulch.
Use one of the branches on her, then speak to her a few times. Eventually she'll ask you for some clothes and a menu will open up. Choose the option to give her equipment, then give her whatever armor you feel you'll never need again, as you can't get back anything you give to her. The Achievement will pop after the transaction is complete.
Note that she'll leave the spot where you revive her and head back to Majula after a little while. You can still give her some clothes in her new position just beneath the obelisk, even if you didn't give her anything during your first meeting.