Cheryl has described feeling "devastated" after Sarah Harding announced her cancer was terminal.
Sarah tragically passed away last September aged just 39 after a year-long battle with breast cancer.
Cheryl, 39, will now join her bandmates Kimberley Walsh, Nicola Roberts and Nadine Coyle to take part in a Race For Life on July 24 in London's Hyde Park.
They will be racing in memory of Sarah in a bid to raise much-needed funds for cancer research.
Cheryl is also trying to encourage others to sign up for the Race For Life in support of those who might be struggling.
"Sarah was such an integral part of us all.
"It is the most natural thing to do for Sarah and her legacy to come together in support of her and others who may be going through the same devastation we experienced," she told MailOnline.
The Girls Aloud gang are also planning to come together to organise a gala dinner in Sarah's honour and have been asking "big companies" to help out.
The money raised from this event will help to fund a crucial study her doctor was working on.
Nadine, 37, said: "Sarah felt really passionately about wanting to help other people in the same situation as her, or who could be at risk of finding themselves in the same situation."
She also said Sarah had wanted to do some fundraising herself but unfortunately wasn't well enough.
Nadine and Cheryl plan to walk the race, while Nicola is set on running it. Kimberley will be abroad on a pre-booked holiday for her mum Diane's 70th birthday but has said she will FaceTime her friends while taking part virtually.
Cheryl recently opened up about their fundraising efforts on Instagram.
She told her followers: "Around this time last year when Sarah was really sick, we were desperately trying to find way to help and comfort her. You feel so helpless at times like that."
"We've decided to do Race for Life for Sarah at Hyde Park on 24th July," she added.
"I know so many of you want to support her and we'd really love it if you could join us. Walk with us for five miles, but also don't worry if you can't join us, people are doing it virtually too.
"I hope to see you there."
The link to Race for Life for Sarah can be found here.
