In addition to their professional relationship, Cullen acted as a friend and confidant to the British star.
However, the two decided to part ways in 2023, with Cullen taking time off from the sport to enjoy some solo adventures.
Who does Cullen train now?
The Kiwi could not stay away from motorsport for long, and now trains compatriot Marcus Armstrong in the IndyCar series.
Armstrong, who formerly raced in F2, competes with Chip Ganassi Racing and has openly praised Cullen for the impact she has had on his career.
“She has all the experience in the world. She’s seen championships won, she’s seen how it’s done by Mercedes and all of that,” Armstrong said according to the Associated Press.
“So having her on board is a source of inspiration and guidance and motivation.”
Cullen’s influence has translated on track with Armstrong consistently improving since the trainer joined his camp.
Together they celebrated a career best result for Armstrong in IndyCar, achieving P3 at the Detroit Grand Prix, his first podium in the series.
The pair will be looking ahead to their latest outing at the iconic Laguna Seca track in Monterey, with Cullen posting a picture to her Instagram story, showing some love to the legendary circuit.
The picture depicted Armstrong in his Chip Ganassi race car, the sun blazing on the track as the trainer posted a series of love hearts.
Armstrong will be looking to better his results in Detroit and secure his first career win at Laguna Seca this weekend.