This is odd as I was able to recruit Minthara at moonrise tower when I played it yesterday. Here's what I did.
I played in honor mode, went to the goblin camp headed straight for Minthara, attacked and killed the goblins in her immediate area then I non lethal knocked her out. Proceeded to kill the priestess goblin, and dror ragslin and goblins in their immediate areas. I long rested immediately afterwards. then got close enough to be able to view MInthara and she was up and non threatening. I did not approach her instead headed to free Halsin and proceeded on with the game.
Once I got the cursed lands I headed straight to Moonrise tower and there she was screaming that she "will not be slandered."
Maybe try that method to see if it works for you?
