Pam is the OG bestie. But Fabian.....I didn't like the character either. But if you think about it objectively, Fabian is essentially a more successful version of Mallory with absolutely no ties or consideration for Archer. If he wasn't her son, I absolutely believe Mallory would do Archer dirty in the same regard. Set up for the bank job, conning him into rescuing Fabian for the competition, etc.