This merchant is found near the entrance to the Shaded Woods.
*** Spoiler - click to reveal ***She is the person who is embodied in stone, blocking the switch that opens the gate to the Shaded Woods. Once you have a Fragrant Branch of Yore, you can bring her back to life. After speaking with her, she will ask you for some clothing, you can give her any pieces you like, but you will not get them back so keep that in mind. Once you give her a piece for all four slots (head, torso, arms, legs), you will unlock this trophy.