If there is a bug and Edwin won't turn into Edwina, the romance will stop? Or will there be next lovetalks and that quest won't have influence? If there is somewhere the same question asked please excuse me, i didn't found it.
Since the Edwina quest is an integral part of the romance, I'm afraid the romance will stall if you encounter such a bug.
As for guest, who had Edwin fall inexplicably silent - do you have a current savegame available?