Last year she weighed 17 stone 6lb and was a size 22. Just over a year later she weighs 11 stone 8lb and is a size 12-14.
Last weekend she entered the annual Woman of the Year contest for Slimming World in Ireland and won.
It was the first time the organisation, which was established in Ireland in 2009 and has 110 groups in the country, ran the nationwide contest.
Next month she will travel to Britain to represent Ireland, competing against entrants from across that island.
She says her fiancé Padraig McGuinness stood by her through weight gain and weight loss.
“He loved me whatever size I was but I wanted to lose weight for my wedding,” she says. They are due to marry in 18 months.
Eadaoin had tried various diets and eating plans and says it was only when she joined a branch of Slimming World in Dundalk, Co Louth, that she was able to eat what she wanted and still lose weight.
“My mother joined and when I saw the amount of nice, proper food — not rabbit food — that she ate, I didn’t believe it when she said it was okay to eat it all. I joined to prove her wrong,” she says.
In her first week she lost 6.5lb. She believes the Slimming World secret is that “it is not a diet”.
“You change the way you cook and the way you eat. Before, I would not have a breakfast. Now I have a breakfast of fruit because I love fruit. I have one cooked meal a day and last night I had beans, potatoes and eggs.”
Eadaoin says she has always loved chocolate and crisps and is adamant that “every day I have a packet of crisps and a small bar of chocolate”.
Her branch consultant, Karen Daly, said allowing people to have the food they like, while also following the Slimming World advice on food optimising, would help people “remove the guilt”.
“We are normal. Don’t beat yourself up because you ate a whole packet of biscuits. You can do that and then get back on track.”
Last year, Eadaoin refused to go out to a nightclub with Padraig, but yesterday joked about how they went to one only last weekend. And when he wanted to go home she wanted to stay.
She now fills up on potatoes, fruit, vegetables and lean meat and is also allowed her treats.
Eadaoin is quick to say she has not always lost weight.
“Over Christmas I put on 4lbs but the following week I lost 7lb. The night before a weigh-in I don’t panic because no matter what, you still have the support of your local group.”
Since she joined in July 2010, Eadaoin has developed the confidence to return to college and has just begun a course in engineering entrepreneurship at Dundalk Institute of Technology.
“I used to think I was happy but I wasn’t. It is only now I can say I am the happiest I have ever been in my life.”
Whatever the outcome of the Woman of the Year contest in Britain, “I will never ever go back to the way I was. I have lost five stone, 12-and-a-half pounds, and am just one pound off my goal weight. I am a size 12 and I cannot remember how young I must have been to last be that size.”