As I said earlier, we need to wait and see if the kick-out-of-party/camp-through-dialogue option is present in the full release. Arguing anything else in EA is purely academic, imo. If it turns out not to be in the final release, then we can complain, lol. Also, if we kick Shadowheart out, Larian will find a way to give us the MacGuffin when we need it later, with or without her.
If they do add such a simple option (it's in the Pathfinder games; can't be all that complicated), it'd be cool if there was a little bit more depth to it than "Are you sure you want me to leave?" "Y/N," such as the companion asking if there was anything that sparked the decision based on unlocked plot points for the character. What would take it to a whole new level beyond even that is if they could try to negotiate for you to change your mind.
As someone with social anxiety and a fear of confrontation, I'd never be comfortable with using the feature, but I always avoid recruiting characters I don't like in order to circumvent it anyway, lol.
