She started out by refereeing IRFU Tag rugby for a season in St. Mary's and from then she was hooked.
Helen was put in touch with David Keane, then a Referee Development Officer in Leinster, who guided her through the first steps and got her on the refereeing ladder.
She is now ready to complete her Level 3 refereeing course under the auspices of David O'Brien, Leinster Referee Development Officer.
Recently she took charge of the uncapped international between the Ireland and Spain Women's team as part of a warm-up for the Women's RBS 6 Nations Championship.
O'Reilly started out with games in the Women's All-Ireland League - her first official game was Dublin University against Navan.
Helen is now into her second season of refereeing men's games up to J1 Level including the Leinster League. She has also been a touch judge in the Ulster Bank League.
Asked about the initial reaction she got from the male players, she said: "I did get a few odd looks in my first season but once I showed that I had the knowledge of the game I think I proved myself.
"Now I'm in my second season and have referred all of the sides at least once. I'm accepted as just another referee."
She received a real boost after one game when approached by an elderly club member who told her that he was thrilled to see a woman in charge of the game and that she had done an excellent job.
"It was lovely to hear that from him. I knew I was on the right track when he told me," she remarked.
And would she encourage other women to get involved in refereeing? "Absolutely. The backing is there from the IRFU. Owen Doyle, the IRFU Director of Referees, gave me huge support and the Referee Development Officers are so generous with their time and knowledge.
"I loved playing rugby and I wanted to put something back into the game. When Owen told me I had been selected for the Women's RBS 6 Nations panel I was really honoured and humbled. The door is open for other women, the support is there. Pick up the whistle!"
O'Reilly will be a touch judge for the Ireland Women v England Women match at Ashbourne RFC next Saturday and will take charge of her first game when England play Italy in Esher on Saturday, March 9.