As someone who played the game, these revelations must be hard to swallow for Iris's alter ego. It's a blow to the stomach to find yourself the 'villain', but now she may find out that she wasn't the villain- rather, the scapegoat. Can't help but feel like the blow being far worse now.
I'd be taken aback with anger. To find your life and the lives of those you once cared for was upturned by an insidious plot. Sounds like an action movie backstory.
She already knew she'd been made the scapegoat in the first chapter, where it had been alluded to and clarified further 'some chapters ago?'.
The complete picture is a lot more complicated tho.
The other nobles that actually bullyed Yuri used her as scapegoat. Whereas Yuri and whoever is behind her wanted to remove Iris, and by extension, the armelia Duke's influence from the royal family and put Yuri in the place of the fiancee to control ed, the heir of her own family participating in the fiasco
against her removed the possibility of retaliation from her household while smearing their name(the Duke's daughter was humiliated in public by the her own fiancee from the royal family and the armelia Dukedom did not do anything so who looks to be in the wrong here?)(and for those aware of Bern's role in that, it would look horrible either way)
Plus the next pope of the church and the next knight order commander were there against her so it also looks like those orgs, along with the royal family, would stand against and show them their place were the armelia Dukedom to step out of the line.
Thats why, sending her to the church as a nun would have been a great idea. It would remove the armelia name from the accused while sending her far away from the accusing party (thus protect her). Though, since Iris still had fight left in her and was very clear headed(not in denial or misery), the duke couldn't do that to her.