I do not think that in that last rather cryptic line she's actually talking specifically
about herself and Prin. The only way the line makes any sense is if you read it as a general reflection on the wider context, of all the dirty mess of the Occupation and beyond that warfare per se
I think it truly hits home to her then that there is no such thing as a "clean" war, that even when the fighting is undertaken in desperate self-defence, innocent people always suffer. Casualties are always
highest among civilians, rather than the actual combatants, because they always get caught in the crossfire. And both sides invariably believe they're in the right, otherwise they would not be fighting in the first place.
who gets involved will have innocent blood on their hands at some point - whether the party in question set out to murder innocents on purpose or not.
So I read her remark as a general reflection on the tragedies of fighting and what it does to people, in which of course she and Prin are both included. He's become deluded and twisted by what has happened to him and Kira is messed up in so many ways she should have had some sort of treatment before even taking up duties on the station!
The first part of what she says I take to refer to the paradoxical fact that it usually takes the very darkest of circumstances to show up the best qualities of courage, compassion or self-sacrifice in people - as "normal life" hardly makes great demands on these. "Sometimes things have to get this bad for us to notice there's any good left in us."
(With the more personal aspect being that Prin could still care about the life of her unborn child, as did she - it was the one impulse they shared, that the child did not deserve
The second part I take to mean that both sides to a conflict are always guilty, yet both try to justify their actions by pointing to reasons why they "have no choice" but to do what they do: because the other side started it; because you're killing our civilians, now we have the right to slaughter yours; because it's a matter of survival; because it's a matter of principle... etc.etc.
(Here again the more personal resonance being that what holds true for both of them is the attempt to justify the unjustifiable - the "good reasons" why they had to kill. And of course they're both at one and the same time victim and perpetrator: the guerilla fighter is an innocent victim of oppression but can't afford to be very discriminating in her attacks, the servant to the military member of an occupation force is an innocent in the wrong place at the wrong time, but has now made himself guilty of deliberate murder.)
So her statement is general but with a personal reflection implied.
P.S. what I found much more confusing was why Prin remained so disfigured in the first place. What with all that advanced medical technology, all these tissue regenarators that seem to be able to heal just about anything, you should think even severe burns such as he suffered should be at least partially correctable. Unless of course on Cardassia, advanced medicine is reserved for military personnel and those of high status, so he simply wasn't important enough to receive much treatment.