"On September 1st, we were among the daily 720 sets of parents to be absolutely devastated with a Childhood Cancer diagnosis," the reality star wrote on her Facebook page. "September is National Childhood Cancer Awareness month. Please take the time to pray for all these children, our sweet baby included. We appreciate each and every one."
Britney Haynes also confirmed the devastating diagnosis on her Twitter page. It is still unclear what type of cancer Tilly has or what the baby's prognosis is.
"Thank you for all of the thoughts, wishes, and prayers for my precious girl," Haynes wrote. "She's everything to me. #PrayForTilly."
Already, some Big Brother fans have set up a fundraising page for Britney Haynes' daughter. The GoGetFunding page has already raised more than $3,200 for Tilly.
Prior to this cancer announcement, Britney Haynes posted several other Twitter messages about her daughter. Several of them involved Haynes' difficulties getting young Tilly to sleep, though it is unclear if Tilly's sleeping problems resulted from her illness.
Just days before the cancer diagnosis, Haynes wrote: "It's 2am and we are definitely driving around town trying to get this fussy baby to sleep. She has to sleep eventually, right??? #HelpMe"
Britney Haynes married Godwin, her high school sweetheart, in March 2012. Tilly is their only child.
Britney Haynes quickly became a fan favorite on seasons 12 and 14 of Big Brother. She made it all the way to fourth place on Season 12 before being evicted by the all-male Brigade alliance.
She then returned last season alongside other Big Brother 15 standouts. Originally, she and fellow alums Dan Gheesling, Janelle Pierzina and Mike "Boogie" Malin returned as coaches, but they later became actual contestants. Haynes did not do nearly as well in her second trip to the Big Brother house, as she was evicted in Week 7.
A very pregnant Britney Haynes also made a guest appearance on the current season of Big Brother. She showed up via video satellite to reveal her baby news and announce a crib-themed challenge. The reality contestant then gave birth to Tilly a few days later.