The two are reported to be close with Cullen not only a physio, but also a good friend and confidant to the seven-time world champion.
Despite the split, the two remain good friends with Cullen deciding to move away from F1 to continue her career elsewhere.
What has Cullen been up to since leaving Hamilton?
Cullen currently works with fellow Kiwi, Marcus Armstrong, a former F2 driver who now races in US series IndyCar.
Armstrong competes for Chip Ganassi Racing, and after a tricky start to the season sits 11th in the driver standings.
The two seem to have a positive relationship with Cullen frequently posting pictures of the pair together in the paddock, training and even enjoying lunch together.
In a latest career update, she posted a picture of the pair following a successful result at the Grand Prix of Indianapolis.
The caption read “Rolling in Red” with Cullen walking alongside Armstrong in a red race suit.
Armstrong finished 5th in the race at the Indianapolis Motor Speedway, a joint best result of the season for the driver.
Next up the pair will conquer the infamous Indy500, part of the Triple Crown of Motorsport, and a prestigious trophy for any racing driver to take home.
Hamilton discussed Cullen and her recent move to IndyCar, praising her as an individual who ‘belongs in the sport’.
"I think she's really enjoying a different environment, but still racing. I think from her time here, she became such a passionate racing fan. I think once you catch the bug, it's hard to get out of it.
"Why should she? She belongs in the sport. She's definitely very, very happy right now."
In addition to this Hamilton hinted at a potential reunion between the pair as he discussed their continued friendship,
"She was and still is a very good friend," he added.
"In fact, we’re talking about getting together again and doing something together soon, like parachute jumping, maybe.
"We’ll never leave each other. I’m very grateful for everything she’s given me."