But to address this, as far as the background we are given, she and a couple of others where memory wiped and send to recover the artifact. Then we meet her and she doesn't really like evil actions. Thats it.
She is someone who spouts the Shar-is-actually-good propaganda and wears a bunch of Shars symbols. She never adapts her propaganda to gain our trust. By all accounts, she is incredibly suspicious. A good Sharran would not be suspicious, which gives -in my opinion at least- credence to the brainwashing theory. Maybe she was a Sharran before that messed up and this is her punishment. But regardless, she is not a real Sharran Priest, she just thinks she is.
I just noticed that she is actually similiar to Lae'zel in that regard - both spouse propaganda and are blind to the true nature of what they endorse. Which is probably the angle to redeem them (harsh reality shock) and also to corrupt them (ease them into the reality). Lae'zel fits better in her respecitve propaganda line, while Shadowheart rather obviously does not.
Shadowheart is really not a bad person at all, and definitely should not be judged based on speculations of potential past crimes...which we don't even know if they happened or to what extent, and much less so if she was under the influence of mind control, which would make her fully innocent. Really I would be surprised if her plot doesn't lead to memory restoration and redemption...assuming you want to redeem her. Which I suspect redeeming her would change her subclass due to the nature of shadow magic and how it works, or doesn't to be more precise, if you are not loyal to Shar.
I'll personally take Shadowheart down a darker path but to treat her as evil from the start of the game is just wrong.
