Just pointing out that any "evil" that shadowheart commited is pure speculation right now. The only thing we know for sure she did was stealing the gith artifact, and we don't even know for sure what this artifact is. Sure she is Shar worshiper, but we have no idea what service (if at all) she provided her goddess.
The talk about atonement is somewhat premature if we don't even know what she needs to atone for
