File on seniority. Don't mention the sex of the driver, it may/may not be sexism, but in the end it sounds like whining. Just saying. The talk should not have occurred in front of the other drivers, but I'd leave that one alone. just file on the seniority issue and never send that kind of message via DIAD again. Be sure, a copy of said message has already been placed in your file.
Favorites are a part of the game. It's not fair, but neither is life.