It's still rather jarring that Shadowheart is dressed up like a crusader for what was a black bag job to retrieve the artifact.
Sharrans are supposed to be devious, a disguise isn't too unlikely. Or did they leap into action in a "No-one expects the Sharran Inquistion!" manner?
After you've sussed her, she could have a "Now you know my secret, allow me to slip into something more comfortable" moment, and out comes the regalia.
There should be an early encounter, before you can trigger the reveal cutscene, where the goddesses and their conflict can be npc-splained. There's plenty of statues and old relics around for that.
