I can't blame her, though. All Nishi can say is Snady will try to double-cross you, which she said she has already figured out. Nishi doesn't know the specifics any better than the greenie does, so really Nishi has nothing to tell her.
Both of them are very ignorant about Snady's current condition and how desperate she is. They think that Nishi is going to be sold off to the highest bidder, presumably Snady, like a slave would be. Nishi no doubt expects she might be forcibly turned into some sort of puppet, or perhaps suffer some other fate worse than death or if she's lucky she might be executed publicly, perhaps, like what happened to the Sargs that were caught. As far as Nishi knows, she is hardly in a position to say, "Tell her I have a rock with her name carved on it!" She can't know that Snady would probably try to earn goodwill by not doing those horrible things.