That is why I find it hard to believe that the actual content of the "building up to a couple" is missing from the game. Why put all the effort in the post-story wrapup and nothing in the actual story ?
So I guess there's a bug that blocks the in-story progress. But how can Larian have missed this ?
I have a feeling the epilogue is supposed to put a band aid over many such plot holes. I think Halsin's thing with the orphans also comes as a surprise if you romance him and he mentions his plan during the Post-Brain-Scene because it doesn't have any build up. Astarion talking about what he did after fleeing from the dock when befriended puts a band aid on that sore spot and Gale doesn't really have a conclusive ending in the game proper either unless romanced or pulverised. So I wouldn't be surprised if if Minthara got the same treatment, though I do hope it is just a bug that gets fixed.
A more general question: If I want to currently recruit her, can I chat with her before knocking her out or will that stop her from appearing at Moonrise? I got a little confused, by what I read on the subject.