The Werewolf curse of the Brecilian Forest is a terrible affliction, and the Werewolf attacks upon the Dalish Camp wind up separating more than one couple. Lost to the Curse, a side quest available soon after you enter the campsite, highlights these problems.
When you're exploring the southern part of the camp you'll likely come across an Elf named Athras. A friendly hunter who does not seem to detest your presence like some of the Dalish, Athras nevertheless seems rather melancholy, as the Keeper Zathrian has ordered all hunters out of the Brecilian Forest. If you're lacking in your persuasive skills you won't find out why this has Athras so troubled.
Manage to dig into him a bit, though, and you'll discover that Athras has recently lost his wife, Danyla, to the Werewolves. Zathrian insists that she is dead, though he refuses to allow Athras to see her body. This leads the Elf to believe that she's been kidnapped by the Werewolves and possibly afflicted by their curse, and though he understands Zathrian's reluctance to allow Athras to ascertain the truth he must know what became of his wife.
At this point, already heading into the forest as it is, you can offer to look for Danyla. Athras will promise a reward in exchange for your services and anxiously awaits your return to camp. That done, you can head out into the Brecilian Forest and resume your normal quest of tracking down the Werewolves in general.
When you reach the East Brecilian Forest you have the option of going in one of five directions once you reach the central area. Opt to follow the northwest passage and you'll find a Werewolf kneeling on the ground and growling in pain. Approach and it will speak, revealing itself to be none other than the missing Danyla. She's in bad shape, as the curse is running rampant in her body and death is on its way.
She has one last request: end her suffering quickly, and return to the campsite with her scarf and love for Athras. At this point you can goad her for a bit of information on Witherfang, learning more about the Werewolf problem in the process, though you won't learn much before she insists on death. You can agree to kill her quickly, after which she thanks you, or refuse and have to fight her to the death. Trying to take her back to the camp results in a fight as well.
In either case you'll gain her scarf. Return to the Dalish and speak with Athras, though do so with Leliana in your party. Tell him Danyla was a Werewolf and has since been put out of her misery and he'll give you an amulet in exchange for the scarf - but only if Leliana is in the party. You can use this amulet to barter with the Mad Hermit. (Alternatively, you can trade the scarf to the Hermit.)