I found another potential bug with this quest. Working with patch 1.02 installed. I went to the tavern and saw Isabella have her little fight. Spoke with her and was given her quest. I than ran around and did other things. I came back to the Hanged Man and Isabella had a quest marker on her head. I engaged her in conversation. At that point, she drew her blades and began to run off fighting as if she was in Hightown.
I have been to Hightown at night and I see Isabella in the plaza, however, when I speak with her, she just spouts something random about the people of Hightown.
I have only just discovered this and haven't begun looking for a fix yet. Still, I thought that it should be noted.