Girls Aloud star Nadine Coyle said her bandmate Sarah Harding faced her terminal cancer diagnosis with courage and bravery.
Tragic Sarah died at the age of 39 from breast cancer this month.
Sarah revealed last August that she had been diagnosed with terminal cancer that spread to other parts of her body.
And earlier this year, Sarah said doctors told her she would not see another Christmas.
Nadine, who sang alongside Sarah in Girls Aloud for almost 20 years, said she faced her illness with "immense bravery" and is greatly missed.
Nadine said: "Sarah was the life and soul of the band. We laughed together, performed together, and grew together.
"Sarah was so much fun and a great friend, always. I’m truly devastated that Sarah has passed.
"She went through the last year with grace, courage, and immense bravery and I already miss her so much."
Nadine, who is set to be a judge on the Last Singer Standing on RTE One later this autumn, added: "I have treasured memories of so many great times together that I will cherish always. May she rest in peace, my forever beautiful friend.”
Before her untimely death, Sarah told her fans that she said she didn't want to know her exact prognosis and just wanted "comfort" and to be "pain-free".
In an extract from her memoir published in the Times earlier this year, she said: "In December my doctor told me that the upcoming Christmas would probably be my last."
Sarah also wrote in her autobiography, Hear Me Out, about how she initially put off getting medical advice when she first found lumps under her arm in December 2019.
She eventually saw a doctor who advised her to schedule an MRI scan - but then "coronavirus hit and everything either went into slow motion or stopped altogether".
She said: "I was aware that I needed to get this health issue sorted, but with everything that was going on, it was tough."
She said the pain continued getting worse.
Sarah said: "One day I woke up realising that I'd been in denial about the whole thing.
"Yes, there was a lockdown, yes, there was a pandemic, but it was almost as if I'd been using that as an excuse not to face up to the fact that something was very wrong."
Proceeds from Sarah’s last single are to be used to fund research by the cancer treatment centre that cared for her prior to her death.
Her final release, Wear It Like A Crown, topped the iTunes chart in March, with all profits going to the Christie NHS foundation, which runs the Christie hospital in Manchester where she was treated.
The Christie said the money will be used to fund research into preventing breast cancer among women aged 30-39 who have no family history of the disease.
