She will. Even Rupert acted twice.

[so she's sure that byleth will kill again if she's not stopped, because whatever prompts them is stronger than her kindness. still, she frowns.]

... she's dear to people too. I... can't and won't do anything to her, and I won't ask anyone else to act on my behalf. Even if only for Dimitri.

[ . . . ]

But she did kill Crow, after having the nerve to shed tears at me over what it means to be afraid to lose. So as far as I'm concerned, she made herself my enemy knowingly.

[and dimitri is arguably the only reason why iris isn't on the fucking warpath]