The celebrity stylist and her once-beloved right-hand man Brad Goreski have not been on speaking terms since they parted ways in 2011.
And a source close to her told RadarOnline that she thinks the timing of his show - now in its second season - is 'tacky and in poor taste.'
Hard feelings: Rachel Zoe is 'furious' at the TV execs who scheduled her former assistant Brad Goreski's reality show, It's a Brad, Brad World, to air directly after her own
'The two had parted on good terms initially, but she felt he was very shady about branching out on his own as a stylist and then getting his own reality show.'
On The Rachel Zoe Project, Mr Goreski told his boss that he was leaving the show to get out of the limelight - not to launch a solo career.
But she soon learned that not only had her former ally acquired her client Demi Moore as one of his own, but he was also launching a reality series on the very same network as hers.
The style expert apparently fears that by making her ex-assistant famous, she also created 'a backstabbing monster'.
The petite 41-year-old fumed during one episode: 'Of course within a week of us parting, [Brad] started to pursue our clients, going to all these events, and doing all these things he said he wasn't interested in.'
Former best friends: After Mr Goreski (left, with Rachel Zoe in 2008) parted ways with the stylist to launch his own career, she accused him of trying to steal her clients
'That's not the truth,' he told The Daily Beast in 2011. 'And she knows that's not the truth.'
He continued: 'I didn't even say goodbye to a lot of her clients because I didn't want anything to be misconstrued as me soliciting anybody.'
But according to RadarOnline, Ms Zoe's suspicions about him are not unfounded.