My favorite andor headcannon is that mon mothma doesn't ACTUALLY know that vel was on aldhani until cassian tells her during her extraction. I mean, she has her suspicions in season 1, but vel never confirms it.

So just imagine for a moment: mon mothma after everything that happened at the senate, with andor and the ghost crew, finally arrives at yavin 4 and the moment she sees vel she's like YOU LIED TO ME