This is a full walkthrough for the Hunt the Devil Side Quest.
The quest takes place north east of the blighted village marked here as well as in the town just north of this location also marked.
If you found her and spoke to her first, your next step is to meet the people hunting for her. They are located just north of this spot in a small town.
If you choose to kill her then you’ll discover she does have infernal drawings on her body. Bringing back her head with reward you with the Sword of Justice. The sword grants the user access to the Tyr’s Protection Abjuration.
Rejecting their offer will initiate a fight, the fight itself is pretty easy and looting Anders will allow you to obtain the Sword of Justice.
Defeating the group and returning to the tiefling will complete the quest and reveal some backstory for our new friend.