I'm going to warn of spoilers, but not use that black text thing. I find it a bit annoying.

Ugh. This stuff is always so frustrating. You don't have a save game from before entering the last portal in the dead lands, do you? That would be easiest. Once you set LastStage to 10, you have to talk to her, she won't talk to you again. BUt I have no clue where she could've gone...
And I'm pretty sure you don't have the Summon Wintermoon spell, correct? Not sure what to do...
-Middark
I mostly use black text when it does contain even a little bit of spoilers - from my own experience I can tell that it's really easy to ruin surprise by giving hint like "after she died" or "after she was resurrected". Well, I guess this doesn't really need it, so I give up from using it.
I have, but it doesn't change the result. Whatever I do, she doesn't say anything and disappears after I leave the house. However, while I was doing some quest she ran from the forest and started following me - and tried to talk to me without any real dialog. After I fast traveled she vanished again. Pretty strange (and yeah, I don't really have that spell, sigh).
I don't know if this helps, but when I tried to find out the source of problem, I noticed that my quest didn't update after I left from the dead lands. It still does say stuff like "Yurn sacrificed himself, this place is tearing apart, I hope that she is still watching me". Is there code to complete quest or something? I am not sure could that even help, though (I don't know much about moding and stuff :E).