Rodrigo, 25, starred in the 10th series of BB in 2009 but now lives as a woman called Rebekah Shelton.
Friends of Rebekah announced the news on Twitter, urging fans to pray for their poorly pal.
"The doctors found a head tumour and she is in com[a]. We cannot speak anymore. Please just pray for our Rebekah," the message read.
Rebekah came fifth in BB and started dressing as a woman soon after. In March, she had a boob job then, last month, Rebekah spoke about how the reality show had changed her life.
"The UK gave me the gift of my life in 2009," Rebekah tweeted. "BB wasnt only about being on TV, it was all about acceptance. Being accepted by another nation.
"A nation that accepted me for who I was without caring about my sexuality, language, etc."
She continued: "People who watched the show back then could see that I wasnt a bad person, I just had a bad temper sometimes. Hopefully everyone noticed that I have a good heart.
"I'm saying all that because it means the world to me when I receive nice messages from my British friends. I will always love Britain.
"I'm going through a difficult time atm but this is the journey to be the person I want and achieve my dreams. Your support keeps me strong. tk."