Another thing about Shadowheart/Halsin that makes no sense to me is that she is in a vulnerable position. Halsin is introduced as a wise druid who cares about the well-being of others. Shadowheart is brainwashed and naive. And when she learns the truth she's in a fragile state. Why would a kind-hearted, mature druid take advantage of her for a cheap thrill? The answer is, he wouldn't. He'd want her to heal, get to know herself and grow.
I haven't romanced Shadowheart, nor will I ever, but I can understand this is double salty for players who do and then have Halsin insert himself into that relationship.