Yeah I honestly don't understand what's going on. It's like her dialogue is load-bearing for the entire rest of the game's stability and fixing it TOO WELL will cause the game to spontaneously combust. I don't necessarily want to assume they're liars, if they say they think she's working it's likely one of their dev builds DOES have her working. But for whatever reason something specific to Minthara continues to mess up between their dev build and being patched to the live build.
It has happened so many times now that I truly cannot fathom the explanation, especially since relatively simple flag activations manually with a mod have tended to cause her to work properly when Larian just cannot ever seem to take that final step to full proper functionality.