Eleanor Walsh and Jillian McNulty were the closest of friends. They were the same age and they shared a wicked sense of humour. They were so devoted to one another, they were like sisters, and Jillian was utterly devastated when six months ago, Eleanor died at the age of just 37.
But in fact, they had never met.
Eleanor suffered from cystic fibrosis, as does Jillian, and thanks to both women's compromised immune system, doctors banned them from meeting in person.
Instead, they exchanged thousands – 35,000, by Jillian's reckoning – of emails and Facebook messages, sent from their hospital beds in St Vincent's in Dublin.
Separated by just a few walls, they'd joke about the hospital food, and support one another if either was feeling low.
For both Eleanor and Jillian, isolated by illness from the outside world, those emails, texts and phone calls were a lifeline.
"We couldn't meet up and socialise, but that didn't matter," says Jillian. "It's hard for healthy people to understand how people who've never met can be that close. But she was lovely. She was just the kindest person you could ever meet.
"She never had a bad thing to say about anyone. She was so kind that she actually wrote books for kids to help them understand cystic fibrosis better, which she won an award for.
"It's fine for adults – we can accept that we have the condition – but kids have a difficult time understanding why doctors are constantly sticking needles in them. So Eleanor wanted to do something for them."
Cystic fibrosis (CF) is an inherited chronic disease that primarily affects the lungs and digestive system. In Ireland, about 1,200 children and adults are living with the condition.
According to Cystic Fibrosis Ireland, the impact of CF can vary. While some people with CF die in their teens, others can live into their fifties.
Sadly, Eleanor was not so lucky. Jillian was just a few rooms away in St Vincent's when she died on December 3, 2012. "A few days before Eleanor died, we spoke on the phone for about 20 minutes," Jillian recalls. "She said, 'I am not good, Jillian'. I just said, 'Look, chick, you'll be grand, think positive'. But she said, 'No, it's not good'.
"I knew she was going to die, but I was still hoping for a miraculous recovery."
Poignantly, it wasn't the first time Jillian had watched a close friend die. "I've had plenty of friends who've been fine one day, and gone a week later," she says. "For that reason, a lot of people say you shouldn't be friends with other CF people, as it's too hard. But while we're not all the same, we understand what the other person is going through."
That bond with other people who can relate to the challenges of chronic illness is a special source of support for Jillian. While she has a close circle of good friends outside the CF community, she admits she struggles to keep up with their lifestyles.
"They understand that I can't do what they do. I can't keep up with their pace of life," she says.
Romantic relationships can be hard, too, and Jillian says she has struggled to find a partner who can take her illness on board.
"Men can get scared with CF," she says. "They don't want to know about it. They can't cope with you being sick or in hospital. People like a stress-free life, and being with someone with CF is a big commitment."
In the circumstances, the relationship between Jillian and Eleanor was all the more poignant.
"When Eleanor died, the nurse came in and she was crying. She said to me, for two girls that have never met, the bond between you was amazing."
Still ill in hospital, Jillian couldn't attend Eleanor's funeral. But once she was well enough to go home again to Longford, she tried to get her life back to normal, jogging and cycling as much as possible to keep her lungs in good shape.
'How much exercise you can do depends on the severity of your CF. Put it this way: I am not out sprinting down the street. I go very slowly, in comparison to a healthy person," she says.
"Half the time I am coughing and people are stopping to ask if I'm okay! But I know I am lucky that I can do so much, a lot of other CFs I am aware of can't do as much. Some people can get bitter and angry towards me because of that.
"My life is as normal as it can be. But before I can even walk out the door in the morning, I have two hours of medication and of therapy to clear the mucus from my chest. But when I'm not in hospital, I'm off doing everything that I can do. I like the sun a lot so I go away as much as possible. And I go to concerts and to shows. You can't live in a bubble."
Jillian is so determined to live as full a life as possible, last year she completed the Dublin marathon, an amazing achievement, and last Friday, on what would have been Eleanor's 38th birthday, she set off from Carrick-on-Shannon on the first leg of a four-day cycle that finished up at the front doors to St Vincent's Hospital.
Joined by Eleanor's sister Maresa and her friend Michelle Doherty, the three were on a mission to raise funds for Cystic Fibrosis Ireland and for St Vincent's.
It was a huge challenge, but Jillian's motivation to keep going was the memory of her friend Eleanor, and her unwillingness to let her illness get the better of her.
"To be honest, death does scare me, and it makes me fight that little bit more. Hence the reason for getting on the bike and for keeping as fit as possible. I will stick at it for as long as I can."
To donate to Jillian's fundraising initiative, log on to http://bit.ly/jilliancharity