For me the same.
I did these steps in Act 1:
1. Talk to Minthara and promised that I will talk to the prisoner.
2. Freed Halsin and start to attack the Goblins
3. Knocked out Minthara. She got the status "Permanently Knocked out"
Now I'm in Moonrise Tower and there is no Minthara. Only the goblin from the Windmill in the destroyed village.
Is this a bug?
In the news pages there was only written that I have to knock her out when I attack the goblin leaders. No other steps.
Apparently if a permanently hostile character is knocked out, the game counts them as dead. So for this method to work, she needs to have the 'temporarily hostile' status, because then the characters count as ok. A temporarily hostile, knocked out character, should be back up after a long rest.
