Having started as his physiotherapist, Cullen and Hamilton became close friends, with the Kiwi often by the Brit's side in and around the paddock on a race weekend helping him prepare for a grand prix.
Then, in 2023, shockingly, Cullen and Hamilton split, with both parties going their separate ways, but crucially maintaining their close friendship.
Cullen deletes Instagram
This was evidenced by the case that Cullen occasionally took to social media to celebrate Hamilton's successes on track.
Last season, for example, when Hamilton won the British Grand Prix at Silverstone, Cullen wrote on Instagram: "Biggest congrats .. epic win !!"
"Lewis, Bono and the entire MB team. Enjoy this special moment. So deserved.
"One of life’s greatest pleasures is having the courage to fulfil your greatest potential. So inspiring @lewishamilton."
Now, however, messages like that and life updates from the Kiwi appear a thing of the past, with Cullen appearing to have deleted her Instagram account.
The reason that Cullen has decided to take this step is unknown. However, it does come just days after a post on social media led to widespread speculation that she was set for a reunion with Hamilton at Ferrari.
Skiing in red, Cullen posed on a slope, with a signpost in the background having the number 44 on it — Hamilton's race number.
This sparked a frenzy among eagle-eyed Hamilton supporters and thus speculation over a potential reunion.
At this stage, however, there have been no reports of this being the case.
It remains to be seen whether or not Cullen's decision to remove her account from the social media platform is a temporary or permanent measure.