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The 39-year-old wrote on Instagram: "Beautiful Sarah this hurts so bad. 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.
"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."
Sarah's mother Marie announced yesterday that the singer had died, after being diagnosed with breast cancer.
Posting a picture on Sarah's own Instagram page, she wrote: "It’s with deep heartbreak that today I’m sharing the news that my beautiful daughter Sarah has sadly passed away.
"Many of you will know of Sarah’s battle with cancer and that she fought so strongly from her diagnosis until her last day. She slipped away peacefully this morning.
"I’d like to thank everyone for their kind support over the past year. It meant the world to Sarah and it gave her great strength and comfort to know she was loved. I know she won’t want to be remembered for her fight against this terrible disease – she was a bright shining star and I hope that’s how she can be remembered instead."
Other members of Girls Aloud have also paid tribute following the tragic news.
Nadine Coyle wrote: "I am absolutely devastated. I can’t think of words that could possibly express how I feel about this girl and 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!"
Nicola Roberts added: "I can’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. There are so many things to say and at first it felt to personal to put them here and then I remembered that there are so many other people grieving her too.
"Electric girl, you made us. You gave it everything and still with a smile.
"A white butterfly flew past my window this morning before I knew, it must have been you."
Sarah first found fame in 2002 when she became one fifth of Girls Aloud - alongside Cheryl Cole, Nadine Coyle, Nicola Roberts and Kimberley Walsh - after auditioning for Popstars: The Rivals.
The band split in 2009 but were reunited for a reunion in 2012.
If you have been affected by this article and want support, please head to Breast Cancer Now here or call 0808 800 6000.
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