Sarah Harding has shared a message of thanks for the "love and support" she has received since revealing she has cancer.
The former Girls Aloud and Celebrity Big Brother star, 39, said she "can't deny things are tough right now".
Harding previously said in August she had been diagnosed with breast cancer, which had spread to other parts of her body.
On Thursday she tweeted: "Hi everyone. Thank you so much for all the messages of love and support that I've received since my last post.
"Everyone has been so kind and reading your comments and DMs has been such a huge source of strength to me.
Hi everyone. Thank you so much for all the messages of love and support that I've received since my last post. Everyone has been so kind and reading your comments and DMs has been such a huge source of strength to me. pic.twitter.com/UGbuoEKpBX
— Sarah Harding (@SarahNHarding) December 3, 2020
"I can't deny that things are tough right now but I'm fighting as hard as I possibly can and being as brave as I know how."
Harding also said she has been asked to write an autobiography.
"It came at such a good time as it's given me something fun & positive to focus on while I've been stuck at home in between trips to the hospital for treatment," she said.
"I've nearly finished it now and this week Mum and I have been looking through old photos, choosing which ones to include."
She shared the news alongside an image of her as a child, as well as an image of what appears to be the book's cover.
Harding rose to fame alongside Cheryl Tweedy, Nadine Coyle, Nicola Roberts and Kimberley Walsh on ITV's Popstars: The Rivals in 2002.
Girls Aloud went on hiatus on 2009 before splitting in 2013.
Harding won the 2017 edition of Celebrity Big Brother.
She made her stage debut in Ghost – The Musical in 2016, a retelling of the hit 1990 film Ghost, which starred Demi Moore and Patrick Swayze.
Harding later appeared on Channel 4 reality show The Jump, on which she suffered a knee injury and was forced to pull out.