It's something of a mystery why even Valeris knew about the conspirators. What was her all-important need to know?
She would have been amply motivated if Cartwright told her that firing at Gorkon's ship was for the greater good of the UFP. Cartwright might further tell her that Chang was in on it and helping to assassinate Gorkon (but that Cartwright would eventually backstab this despicable enemy, so no worries). But what would be the point of telling Valeris that the Romulans were involved?
I guess it's just a bit too weird for my tastes that an operative very high in the ranks of the conspirators would be sent to Kirk's ship where she could get captured, either by Kirk or (more worryingly) by the Klingons. Goons like Burke and Samno, yes. Their handler, yes. But why would the handler need to be so knowledgeable? Perhaps Cartwright just wanted to limit the number of middlemen...