Quickly revealing her talents at local level, she joined the Football Association of Ireland Referee School of Excellence.

She was an assistant referee alongside Irishman Neil Doyle for a qualifying match between FCI Levadia Tallinn and Slavia Prague.

She was called for the second time to the Women's World Cup a year later,[10] covering four games alongside French referee Stéphanie Frappart,[11] with group ties Argentina versus Japan, and Netherlands against Canada, the quarter-final between Germany and Sweden, followed by the final, with the United States beating the Netherlands 2–0.

[14] A few days earlier, on 9 August, as preparation, Michelle had joined the duo of French women to referee a Ligue 2 match between Guingamp and Orléans.

[18] In November 2024, it was announced that O'Neill would run as a Fianna Fáil candidate in Wexford at the 2024 general election.