If its the quest I think it is should be a couple dead bodies in the area your sent to you need to stand near them for her to appear and run over to you.

I had this same bug and had to drop the quest and pick it up again. I found her in the right spot the first time but it never completed talking to her, even though I did several times. Then she just disappeared and the quest marker moved to across the river.

What I found was I had to choose the right dialog or it didn't fully complete the step to talk to her. I had similar problems with conversations with King Emeric and the Prince in that chain. There are multiple options to talk to them about but most of them just take you around in circles.