Lottie Tomlinson was seen with Piers Morgan's son on a boat after reports of growing close to Caroline Flack's ex Lewis Burton.
The One Direction star's sister, 21, took to Instagram on Monday to wish Spencer a happy birthday with a clip of the pair riding the waves.
She posted stunning footage from their outing when she was in Saint Tropez last week to mark her friend's birthday online.
In the sun-soaked clip, Lottie posed in a triangle top black bikini while Spencer was shirtless for their fun-filled day out.
Her golden waves spilled over her shoulders as she showcased her fantastic figure in a two-piece swimming gear.
The friends had big smiles while they enjoyed the scenic boat ride just off the coast of Saint Tropez, in the south of France.
She wrote: "Happy birthday spendog." (sic)
It comes after Lottie was spotted with Lewis following reports the pair had grown close.
Claims emerged the duo had bonded over recent tragedies - Lewis lost his ex Caroline Flack while Lottie had both her mum Johannah Deakin and sister Felicite die.
Lewis was heartbroken when Caroline took her own life aged 40 at her north London flat five months ago.
Lottie was devastated over her mum Johannah losing her battle to leukaemia aged 43 in 2016 and losing her younger sister Felicite in a drugs overdose.
Claims surfaced they were first thrown together at a house party hosted by Caroline's BFF Lou Teasdale three months after the Love Island presenter's death.
A source told MailOnline : "They have been meeting up in secret for weeks but their newfound friendship hasn't gone unnoticed by mutual pals.
"Not all of Caroline's friends are happy with how the situation appears to be developing but can understand that both Lottie and Lewis have been there for each other as a shoulder to cry on.
"Lewis spent last week in Marbella while Lottie was in St Tropez the weekend previous, they couldn't wait to be reunited with each other on Friday."
Mirror Online previously contacted reps for Lewis and Lottie for comment.
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