Best-known for appearing on the reality TV show, before her transition in 2009, she she came fifth on the tenth series of the show, competing under her birth name Rodrigo Lopes.
A statement posted by her social media account said she had "died unexpectedly on Wednesday night."
It was unclear who posted the message.
In 2016 she appeared on courtroom reality show Judge Rinder where she revealed she had undergone16 surgeries during her transition.
"It's hard. Nobody will choose to go through the hardest path," she said. "Nobody wakes up one day and says, 'Yes, today I'm going to be a woman,' or, 'Tomorrow I'm going to be a man.'
"It's a hard decision because first you have to face yourself, because it's not easy to be a different person or what's considered different. Then, you have to face your family, you have to face society, you have to face jobs, because people don't give opportunities.
"So that's why I say people think it's easy. People think, 'Oh, she looks good now, she can go out and have sex with guys or get married,' but people don't know the journey I've been through.
"I've been through the worst three years of my life."
She added that she "regretted" her gender reassignment surgery.
"I saw that horrible thing between my legs and I started crying around the hospital saying, 'I regret, I regret,'" she said. "I wanted to kill myself because it was a nightmare."
In a separate interview with OK! Magazine she revealed that her family had a hard time coming to terms with her transition.
"The only think I wish is that my family will learn to accept me," she said. "At one point before my surgery I had to leave home and for six months of my life I turned to prostitution.
"So many times I wanted to kill myself because I had no one to talk to. It was a big step to go full time as a woman. It's different when you are having fun with your friends in the clubs to changing your whole life and facing the rejection or acceptance of the world."
Although she was not a regular Twitter user, one of Rebekah's most recent posts appeared in June 2015.
"I'm sending this tweet to you people who still like me for some reason. People from the UK who always loved and accepted me for who I am."
After the announcement about her death was posted to the social media site, tributes poured in for her.
"What a way to leave the world – being who you truly are, finally, having being hidden in the wrong body. Such a role model to many and great laughs on Big Brother."
Another said: "I remember watching her on Big Brother a few years ago and I loved her personality. She achieved so much through her transition."
Rebekah made history during her time on Big Brother, forming the show's first-ever same-sex relationship with fellow contestant Charlie Drummond. The pair continued their on-off relationship after the show.
An account believed to belong to Mr Drummond wrote: "My heart is broken forever. We had so many plans. We shared probably [the] biggest experience of our lives together. Thoughts are with your family."
Gerry Stergiopoulos, who appeared on the eight season of Big Brother, said: "For ten years Rebekah Shelton has always been there for me. Right now I'm feeling devastated. I hope I will wake up soon and this was all just a bad dream.
"The most beautiful smiles hide the most terrible secrets. The kindest of hearts have felt the most pain."
If you have been affected by any of the issues mentioned in this piece, contact Samaritans on 116 123 or Switchboard on 0300 330 0630.