I don't think you need to talk to her, but she's on a wooden pier at the village south of Morkul.
She tells you she saw it at sunset and that you should take some friends if you want to catch it. What I did was get 2 more people during in-game night time. Caught it about 10 mins later. Everyone in the group got the fish from the same hole.
UltimaJoe777 wrote: »So fish appear at certain times of the day now eh? Good to know.