I freed the slaves and killed the slavers. No, I've never talked to Aeldys.
EDIT: There's a new twist to the problem. After finishing some unrelated quests, I received 3 letters, nearly one by one, 2 from Aeldys and 1 from Furrante. I'm going to check upon them.
EDIT: I've been to Aealdys. She was happy I had killled the slavers and gave me a mission to spy on Furrante. And after speaking with Furrante, A Shrewd Proposition has been finished. So, the letters were just delayed, somehow.