I'm thinking in terms of the writers creating motivations for her to be insecure though. She wouldn't have seen the two of them together, and while weeks or months passed that might leader her to believe that he's hooking up with Genesis, as the audience we don't see any of that.
It's literally one episode between Caleb being forced to hang out with Genesis because she snuck back into the academy and then drunk Tarima accusing Caleb of infidelity. Even the Riker-Worf-Troi dynamic had a few episodes to develop before leading to a bitter (heated) rivalry in All Good Things.