Grahame was known for starring in the seventh season of Big Brother in 2006, which was won by Grahame's ex-boyfriend, Pete Bennett.
She also came second in 2010's Ultimate Big Brother.
Following the tragic news, Davina McCall - who presented the show during its run on Channel 4 between 2000 and 2010 - tweeted: "I am so desperately sad to hear about Nikki Graham.
"My thoughts are with her friends and family. She really was the funniest, most bubbly sweetest girl."
Some of her former Big Brother housemates also paid their respects online, with Glyn Wise, the runner-up of the series, referring to Grahame as a 'true icon'.
Beyond Upset! Devastating news about the passing of Nikki Graham. A true icon and the real winner of Big Brother 7! I will always remember your laughter, your smile, your tantrums and bluntness. But more than anything I'll remember your zest for life. I love you always Nikki xxx pic.twitter.com/XYRFBojmNb
- Glyn Wise (@GlynWise) April 10, 2021
He wrote: "Beyond Upset! Devastating news about the passing of Nikki Graham. A true icon and the real winner of Big Brother 7! I will always remember your laughter, your smile, your tantrums and bluntness. But more than anything I'll remember your zest for life. I love you always Nikki."
Aisleyne Horgan-Wallace, who came third, also shared a photo of Nikki, writing: "I can't [breathe]."
Fellow reality TV star Mario Falcone, of The Only Way Is Essex, also said: "RIP Nikki Grahame. Sad news. Just 38 years old."
Jedward, who starred in the celebrity version of Big Brother in 2011, sent their love to Grahame's family and friends.
They said: "Rip Nikki Grahame as fellow Big Brother contestants we've gone through the same experience and having met you on TV shows! Our heart goes out to your family and friends."
Grahame sadly passed away yesterday (9 April), with a representative for the star saying in a statement provided to LADbible: "It is with immeasurable sadness that Nikki Grahame passed away in the early hours of Friday 9th April 2021. Please respect the privacy of Nikki's friends and family at this tragic and difficult time."
She had checked into a private hospital last month to seek treatment for her eating disorder.
Appearing on This Morning last week, her mum Sue said the pandemic had left her feeling 'cut off', especially with the mandatory closure of gyms.
She said: "With Covid, it sounds crazy but stuff like gyms closing impacted her.
"In order for her to eat she needs to know she can exercise, so when they closed it was quite a worry, the isolation as well.
"I asked her if she would come and stay with me but she said she needs to be in her home.
"She was [suffering terminal loneliness] she felt very cut off and spending too much time on her own with not enough to think about other than food.
"It all came to a grinding halt. Also for Nikki, she would muddle herself through the year knowing she's got friends abroad and she would visit them.
"She spent a lot of time last year cancelling holidays."
Featured Image Credit: PA
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