The 61-year-old Nolans singer has been diagnosed with incurable liver cancer - the third time the illness has returned following her initial breast cancer diagnosis in 2006 and a secondary cancer on her pelvis in 2017 - and in the wake of Sarah's brave health admission last week she has offered her support to the former Girls Aloud member.
Writing in the latest issue of New! magazine, Linda said: ''Sarah, I was so shocked and devastated to hear about your breast cancer diagnosis.
''If I can say anything to you, the support you'll get from the public will be amazing - it was overwhelming for my sister Anne and me.
''People are genuinely lovely and want to wish you the best. Initially, I didn't want people to pity me, but it was weight off my shoulders when it came out and I hope you're feeling a sense of relief too.
''This is my third time of being diagnosed with cancer now and each time is just as scary.
''But once you get your head around it - and you've got a supportive family, which I know you have - before you know it you'll be at the end of your chemo treatments.''
Linda - whose sister Anne was diagnosed with stage three breast cancer in April during the coronavirus lockdown - also gave Sarah tips on how to cope with the debilitating chemotherapy treatment.
In her letter, she continued: ''I started my chemo in June and thought 'I'm never going to get to September,' and now I've got two treatments left. And you get into a routine with it.
''Although you're feeling rubbish, remember it's treatment to make you better. As you've said, the doctors are amazing and give you so much support, but don't be frightened to ask questions.''
Sarah, 38, took to Twitter at the end of August to tell her followers and fans that she had been diagnosed with breast cancer earlier in 2020 and that the cancer had now spread to other parts of her body.
She wrote: ''Hi everyone, I hope you are all keeping safe and well during these uncertain times. I've not posted on here for so long, thank you to everyone who has reached out to check in on me, it really does mean a lot. I feel now is the right time to share what's been going on.
''There's no easy way to say this and actually it doesn't even feel real writing this, but here goes.
''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.
''I understand this might be shocking to read on social media and that really isn't my intention.
''But last week it was mentioned online that I had been seen in hospital, so I feel now is the time to let people know what's going on and this is the best way I can think of to do so. (sic)
''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.
''In the meantime I hope you'll all understand and respect my request for privacy during this difficult time. Sending you all so much love...X''
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