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Kiely is understood to have handed in her notice since the opening round of the Supercars season in Bathurst, which will end a seven-year stint with the squad.
She joined Erebus in a public relations role back in 2016 before being named General Manager of Communications in 2019.
A year later she was promoted to Managing Director, a role she held until now.
She is expected to attend the Australian Grand Prix with the team for what will be her final appearance in Erebus colours.
The title-winning team has endured a difficult start to the year prompted by an unexpected off-season split with star driver Brodie Kostecki.
That led to a number of major backers also heading out the door, including title partners Coca-Cola and Shaw and Partners.
A new look, with major backing from TFH Hire, was unveiled for the Bathurst 500 where new drivers Jack Le Brocq and Todd Hazelwood ended up 11th and 13th respectively in the standings.
