..first dialogue round says "Trust Shadowheart - do not interfere"...
..but many people also did choose to trust Shadowheart in their first playthroug..
But what exactly are you trusting her to do? To me, trust means expecting someone to act exactly as you hope - and believing they won't do otherwise. Without metagaming on a first playthrough how could you possibly know that sparing Aylin is even an option? In my view "trust" in this situation would be Shadowheart saying to Tav "I will spare Aylin if you want it so much - just give me the spear and let me approach her" - and this is where you trust her. But handing her the spear and saying "do as you wish" while she's practically crackling with the urge to kill Aylin? That's not trust - that's servility.