Junior Later that year, she won the
Provincial Women's Hockey League championship with the Stoney Creek Jr. Sabres. With the same Sabres team, she would also gain a silver medal at the 2015
OWHA Provincial championships. During her final season (2015–16) in the Provincial Women's Hockey League, she was bestowed the captaincy of the Stoney Creek Jr. Sabres. Leading the team in goals, assists and points, she ranked sixth overall in the league. In addition, she was part of the Team Ontario Red roster that won the gold medal at the 2015 Canadian Under-18 Women's Nationals.
College As a freshman, O'Neill ranked second in scoring on the
Cornell Big Red. Finishing as the
NCAA's leading scorer in shorthanded goals with five, she placed seventh in the nation among all freshman with 0.84 points per game. O'Neill experienced greater success as a sophomore. In addition to leading the Big Red in scoring, she tied for the NCAA lead in shorthanded goals, scoring four, while her seven game-winning goals tied for fourth in the nation. Recognized as the Ivy League Player of the Year, she also gained spots on the
ECAC and Ivy League First-Team All-Stars, respectively.
Professional PWHL Montreal of the
Professional Women's Hockey League (PWHL) selected O'Neill in the second round, seventh overall, of the
2023 PWHL Draft. On October 30, she joined Montreal on a three-year contract. At the end of December, O'Neill was named one of Montreal's
alternate captains for road games. During the
2024–25 season, O'Neill scored one goal and five points in 30 games, and in four playoff games added one goal and one assist. Following the season, at the
2025 PWHL Draft, she was traded to the
New York Sirens along with the 28th overall pick in exchange for forward
Abby Roque. ==International play==