I've just reached Act 3 on a Dark Urge/evil playthrough and honestly? There's absolutely no reason for Minthara to be tied to the destruction of The Grove. If we were able to knock her unconcious or talk her down at the Goblin Camp, her recruitment at Moonrise and the subsequent story would not be any different (and what a great story she has!).

There are other characters in our party that are...not great people, and folks have no issue with them being available to recruit. Minthara would also be another good character to work alongside Astarion trying to convince the player on the merits of tadpoling and domination.