In my opinion ofcourse. Anyway, looking at my character her background, this would be an incredibly hard decision.
Her deep hatred for the Thalmor would make her want to side with Kematu, if he speaks the truth.
I find it a bit difficult to believe they are justiciars of Hammerfell considering they are hiding in a bandit hideout.
However, Saadia calls them assasins of the Thalmor. And they certainly don't seem like that either.
It's hard, if she choses Kematu, she would regret it and feel like she betrayed Saadia.
If she choses Saadia, she would also regret it, feeling that Kematu could be right. And that she now abandoned the wish of Hammerfell to see justice against the Thalmor, which is something she would support considering her deep hatred.
Well, here she is then. Staring at Kematu, is he right or wrong? Damn, difficult choise.