An extra-strong bond between the siblings will be sealed next week when one gives the other the precious gift of life.
Diane, 59, is donating a kidney to kid sister Nadine, 55, and admits: "I can't wait to see her back to her old self.
"She has been ill for so long that when I found out I could help I jumped at the chance. This means so much to both of us."
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Nadine was diagnosed with kidney problems almost a decade ago and was told by doctors it could eventually lead to end stage renal failure. Without a transplant the only option would be a life on dialysis.
Diane had a battery of tests and proved a perfect match and so the two sisters will go under the knife in adjacent theatres at Manchester Royal Infirmary on Tuesday morning.
Nadine said: "How do you say 'thank you' enough to someone who is giving you her kidney?
"I'm going to get my life back and it's down to Diane. We've always been very close as sisters, but this brings us even closer, if that's possible."
Diane will be first in theatre and faces the bigger of the two operations to remove a healthy organ. Nadine will follow close behind and surgeons will prepare her ready to receive the kidney as soon as it has been taken out.
While the donor will spend three days in hospital before being discharged, the recipient will stay between seven and 10 days to make sure there are no rejection issues.
"There shouldn't be," said Nadine. "Diane is the best match I could possibly get. I'm very lucky."
Diane admits the surgery is daunting - it will be her first-ever operation.
"Yes, it's a big thing to do I suppose. But to be honest I didn't have to think about it. I'll do anything if it helps Nadine get well again.
"We lost our other sister Julie about nine years ago to cancer and that was awful. So you just do what you can to help each other.
"The renal team have gone through all the risks and I'm well aware of that. I have been ever since me donating a kidney was first suggested 15 or 16 months ago.
"Nadine had the most painful of her kidneys removed in October and she has had to recover from that operation before this can go ahead.
"Her kidney function before that was 12 per cent. Now it's down to five per cent, which is nothing really.
"So the last couple of months have been very tough for her and it's been distressing for me to see her like that. People don't realise the side-effects, like feeling very sick and having terrible headaches because of all the toxins in your body.
"But she has been an absolute trooper. The thing is she will battle on because she doesn't want to worry other people.
"I'v been very lucky with my health and I've never had a stay in hospital, so that's the thing I'm mainly dreading.
"But it's a small price to pay for having my sister back in good health and starting to enjoy her life again. What's six weeks out of my life when Nadine has had 10 years of this?"
Nadine's 21-year-old twins Daniel and Rachel have been home from university for Christmas and she was determined to have a family Christmas Day at home with them and her husband Steve.
"She's been very poorly, but she wouldn't let that stop her - she even cooked the dinner," said Diane. "So one of the things I'm looking forward to is seeing her back to normal and enjoying Christmas next year - I've promised her it will be Party Central here."
The two sisters were brought up in Penwortham, where Nadine still lives. Diane is just up the road in Lostock Hall.
It is expected they will both be out of action for between four to six weeks. But they wanted to share their story with Post readers to highlight the great work being done in transplant surgery, particularly with 'live' donors.
Nadine said: "I feel really strongly about organ donation. Just seeing all those people in hospital having dialysis three times a week for four hours at a time puts this into perspective for me.
"I think it so important that people consider donation. It's not an easy thing when you look at what Diane has had to go through getting to this point as a live donor.
"She's had so many appointments to attend, so many tests to go through. She's been poked and prodded and never complained once."
Nadine revealed her kidney function has been dropping steadily since her first diagnosis.
"Back then it was 68 per cent," she said. "They said I might be fine and lead a normal life, but every time I went back and had it tested it had dropped further and I was getting more symptoms.
"Over the last couple of years I've been really tired all the time and had no energy. In October, when it had dropped to 12 per cent they took one kidney out and told me that within eight weeks they would go ahead with the transplant.
"Diane is thrilled and I'm thrilled that it's going ahead. But on the other hand for me is the thought that she is going through this massive thing for me. It's really humbling.
"I would go through exactly the same for her. She has never moaned once. She's so brave, although she'll tell you she isn't.
"She is the strongest one in the family. She is really selfless - for her it's about doing everything for everyone else. And that shows with what she's prepared to do for me.
"As I said, she's giving me my life back. And, yes, it will be Party Central next Christmas.
"Right now all I want to do is get it over with and start living again. For instance I just want to go on holiday with the twins and spend some time with them where I'm not falling asleep."