They sent letters to each other a couple of times. Many would agree that there is a classic story of the homosexual tensions bubbling just beneath the surface between Hemingway and Fitzgerald, so maybe there you could find room for jealousy. Both of them had strong perceptions of what it meant to be gay, and they stated how to interact with their gay friends. Perhaps if they had worked together, they could have done more for this, let us call it "project".
You use were was doesn't sound right
Tom and Daisy attend a party at Gatsby's place the next Saturday night. Tom has no desire to attend the party, but his loathing for Gatsby makes him want to keep an eye on Daisy.