Sometimes... it's necessary to keep secrets even from people you would trust your life with, for some reason or another. [Unknown to Arturia, Irisviel speaks from experience.] There will be a time where you will be able to tell him everything. I'm sure that, when that time comes, he'll understand.

[Irisviel's hands gently curl into fists as she reminds herself to keep a respectable distance between her and her fiancee. It's one thing, wanting to reach out when Arturia is merely saying upsetting things. But when there is hurt so clear (to the homunculus, at least) on her face? That takes a whole lot more self-control.]