A native of Dublin, O'Shaughnessy won the Girls 2023 Ireland U18 Order of Merit as the country's U18 Golfer of the Year. She had six top 20 finishes during the 2023 amateur season and was the runner up at the Ulster Girls Open, Leinster Girls Open and the Connaght Girls Open.
O'Shaughnessy was a member of Ireland's U18 Girls Team at the 2024 Ireland vs. Wales 2-day International and the 2023 R&A Girls and Boys Home Internationals. She was a member the Leinster U18 Girls Team for a pair of Ireland Interprovincial Championship teams in 2021 and '23.