Prior to that, lovetalks stopped around chapter 3 ~ 4, but since I could still flirt with Sarah I assumed that my romance was alive and she was just scripted not to initiate lovetalks in chapter 4 (which makes sense she we are about to confront Irenicus and all).
In Underdark, however, she stops flirting; instead, when I try to flirt with her, I get the following reception:
I am sorry, CHARNAME, did you need something? I figured we needed to stay focused if we’re going to get out of this alive.
Now, I understand the situation, but this response strikes me as more then a little cold. Does it means that our romance is dead, or it will still continue after the Underdark? (By the way, I can still flirt with her back in the City-of-Caverns, but as soon as we enter the Underdark flirting abruptly stops.)
For reference, our romance progressed just fine in the chapter 2; I can’t imagine any responses that might have killed it, although we didn’t get, ahem, intimate yet. In chapter 3 lovetalks seems to have mostly (or completely, I don’t recall) stopped, beside Sarah’s quest (meeting her mother and acquiring a cure for her uncle), which I naturally completed.
Overall, I am not sure what could have killed our romance, beside, perhaps, not progressing far enough into the romance by the time of Underdark (but I understood that most – or all – other romances continue normally in chapter 6, and don’t require being completed before going after Imoen).