Harding had revealed back in August 2020 that she had been diagnosed with breast cancer which had spread to other parts of her body.
She sadly died from the cancer on the morning of Sunday 5 September.
Nadine Coyle and Nicola Roberts shared pictures of Harding on that day, leaving some heart-breaking comments.
In Coyle’s post she wrote: “I am absolutely devastated!! I can’t think of words that could possibly express how I feel about this girl & what she means to me!! I know so many of you will be feeling this way. For now I’m sending so much love to you!!!”
Roberts shared several photos of herself and Harding together saying that she “couldn’t accept that this day has come”.
“My heart is aching and all day everything we went through together has raced round my mind. Especially this last year since her diagnosis, as hard as the year has been, our new memories are strong in my heart,” she wrote.
What did Kimberley Walsh have to say?
Walsh posted a couple of pictures of herself and Harding together on Instagram the next day, saying that it “hurts so bad”.
A post shared by K I M B E R L E Y W A L S H (@kimberleywalshofficial)
“To wake up and know that you are really gone is too much to bear. Hearing your infectious chuckle was one of my favourite things in the world,” she wrote.
“Your fire burned so bright and you loved, lived and laughed so hard. Sending love and strength to everyone who is grieving today. My heart is broken.”
What did Cheryl Tweedy have to say?
Cheryl Tweedy was also understandably poignant in her post on Instagram saying that although she “knew this day would arrive” that she was still “at a loss for words”.
“As I try to navigate my way through these painfully strange and horribly unfamiliar waves of disbelief & finality I am experiencing, I wanted to extend my condolences to all of our GA fans,” she wrote.
“We were like an extended family for so long and we know so many of you by name. I wanted to make sure you knew just how much your love and continued support meant to Sarah through her most vulnerable times.
“She was so grateful and you really lifted her spirits when she needed you most. I also realize so many will be deeply affected by the circumstances of Sarah’s passing… I am sending you all so much love. I love you Sarah… farewell.”
Girls Aloud were a group that was created in 2002 through the ITV talent show Popstars: The Rivals.
They enjoyed great success, becoming the UK’s biggest selling girl group of the 21st Century, and managed a streak of 20 consecutive top 10 singles in the UK.
They stayed together until 2009, before going on hiatus, briefly returning in 2012 and finally splitting in 2013.