I just ran into the same problem. I need to talk to Viola, but she appears to be stuck underneath Candlehearth. I can see the quest arrow that is supposed to be over her head in the ground when I walk around Candlehearth.
While it does bug me that I spent so much time looking for her only to find her quest arrow stuck in the ground, I suppose I'll just continue on with the game until this gets fixed. I'm also a little bummed that I will not be able to by the house in Windhelm.
You can still buy the house, it is just useless until you finish the quest because you can't upgrade it or anything. I bought the house only to find this out later.
Also, I don't even get a quest marker for her...its like she doesn't even exist in my game. Huge disappointment, because I really want to be able to upgrade/use the house. The armory for it is really nice. (My bf has the game and he was able to buy and upgrade the house...another reason I am so annoyed. LoL)