Kimberley Walsh has revealed she is in constant contact with her former bandmate Sarah Harding, who shared her cancer diagnosis last week.
The Girls Aloud star revealed that she was undergoing chemotherapy after being diagnosed with breast cancer, but that it had spread to other parts of her body.
Kimberley, 38, has thrown her support behind her friend, admitting that the whole situation is "tough".
She said: "I am completely devastated, it's been really, really tough, but speaking to her a lot helps and keeping that contact.
"She knows we're there for her every step of the way.
"She's a strong girl and I love her so much," she added to The Sun.
Kimberley and her fellow Girls Aloud members rallied around Sarah, 38, after her honest statement last week.
Singer Sarah shared a photo of herself in a hospital gown and admitted she was speaking out as she had been seen in hospital.
She said: "Earlier this year I was diagnosed with breast cancer and a couple of weeks ago I received the devastating news that the cancer has advanced to other parts of my body.
"I'm currently undergoing weekly chemotherapy sessions and I am fighting as hard as I possibly can."
Sarah went on: "My amazing mum, family and close friends are helping me through this, and I want to say a thank you to the wonderful NHS doctors and nurses who have been and continue to be heroes.
"I am doing my very best to keep positive and will keep you updated here with how I'm getting on."
After the message, Nadine Coyle replied: "I love you! You have always been able to achieve miracles when needed! I am here for you all the way and always will be."
Call My Name songstress Cheryl shared a simple heartbroken emoji on Twitter.
And Nicole Roberts tweeted: "It goes without saying that this is blindsiding. Sarah you're so loved and supported."