I'm Sorry to say that I do not have any fix to that problem.
It seems like that is the only option that is bugged as well.
I can marry Anora if I let Loghain live.
If I support Anora as sole ruler, even if I kill Loghain, the quest also updates and vanishes from quest log after the post-landsmeet talk with Anora.
However, if I let Alistair kill Loghain, and choose to marry Anora afterwards, she will act as if I did not during the Post-landsmeet talk, and the landsmeet auest is still active after the talk.
I am not in a love triangle (at least I do not think so, I dumped Morrigan for a hardened Leliana)
It would be nice to just get a confirmation from someone that knows for sure if there is a way around it or not.
I just remembered that Anora mentions me being her betrothed during the ceremony at the end, but Leliana will not mention Anora if I talk to her after the ceremony before I leave.
But Leliana mentions Anora if I let Loghain live and the landsmeet quest is gone from questlog.
