Except our characters can become aware of that fact throughout Act 1, especially if you postpone Goblin Camp stuff.
Kill duegar in Underdark, rescue True Soul Nere and you'll have the opportunity to explain to him the effects of the Prism and that cult are basically a front for mind flayers. Even the scene with dying True Soul next owlbear cave and tadpole extraction, Halsin's notes/tadpole sample and dissected Drow corpse in Grove are big "No-No" in regards that the cult can be trusted and that Absolute is a legitimate deity.
So if that stuff works on Minsc (with a bit of persuasion), Nere (passively the moment you encounter him), so it should work on Minthara.
I know. As I already said, that stuff largely depends on how
you play. Most people I’ve seen deal with the Goblin Camp first before they go to the Underdark because of the difficulty jump, and that includes me. It becomes trivial and almost metagamey when you put it like that, but I agree that we should be able to save Minthara with the Prism. If not likely in Act 1, then at least in Moonrise Towers. I'm talking about a hypothetical "good" recruitment here.
I’m still of the opinion that, narratively, it makes more sense for Minthara to be able to flee from the fight at the Grove. Her dialogue prior to the raid has her saying "I do not intend to lead a suicidal charge. The goblins are expendable; I am not." - and yet the outcome of the battle contradicts with that. She just charges in until she dies.
