Baldur's Gate 3's second act has a couple of very important decisions—so much so I wrote a whole dang guide on how to thread its particular narrative needle. Before I get stuck into it, spoilers for the game's second act, in case the headline didn't clue you in.
A Reddit thread optimistically titled "How to bamboozle Lady Shar" by rokamuda (thanks, Gamesradar) lays out how exactly this comedy of errors happened. "I made short work of Nightsong, saw the cutscene of Last Light Inn dome crumbling and got all of Lady Shar's boons … as I exited through the portal I got the cutscene of Lady Shar cursing me for not completing my mission, being marked as the enemy, and Shadowheart asking forgiveness."
Turns out, that's down to the Disguise Self spell. This first-level bit of trickery magic wraps you in the arcane guise of… well, anyone. Its scope is unfortunately a little limited in Baldur's Gate 3, but it does change the context of a few scenes, letting you access different race's dialogue options—some of which can get you into new areas, as long as you go in with a plan. It also lets you Speak with Dead to a corpse if you killed it, since it won't recognise the face of its murderer (bodies aren't obligated to answer questions if they don't want to).
In this case, doing the whole Nightsong encounter as Shadowheart while in disguise seems to nix the "Shadowheart's fulfilled her destiny" tag.
This might be objectively the worst ending to Act 2 you can get. Rokamunda has successfully found a way to screw over the most people with the smallest reward, ensuring Shadowheart gets kicked to the curb by momma Shar. All they got out of the deal was some Dark Justiciar armour—what a lousy deal.
"Ok, so what did you accomplish?" reads one comment, "You pissed off of Shar and destroyed Last Light Inn. Sounds like Shar pulled one over on you." Meanwhile, another player remarks that it's pretty in character for the lady of loss to be peeved that Shadowheart didn't show her actual face: "Checks out. Shar is the pettiest god out there."
At any rate, I think that "no one gets to be happy" run is in need of an update. Poor Shadowheart: abducted to a mindflayer ship, survived a crash landing, had to deal with Lae'zel negging her, overcame a crisis of faith, fulfilled her dark lady's will—all for Shar to abandon her because she didn't give exactly 100%. Girl just can't catch a break.