The midfielder took part in two friendlies, and in doing so eclipsed the record set by Chelsea player Conor Clifford, who played for the boys U-15 team when he was 13.
Under-15 is the youngest age at which players can represent their country at international level in Ireland.
"She's been playing since she was three and has been scouted by nearly every club," her proud father George explained.
"She's currently playing U-14 level football with Home Farm; she's only 12 and she's the only girl on the team."
Footballing talent appears to run in the family -- George played in the League of Ireland for St Pats, Bray Wanderers and Thurles Town.
And Alex's older brother Cian (16) was capped for Ireland's U-17 last month after travelling to Macedonia to compete in the European Championships.
Renowned for her dinky runs and intricate dribbling technique, Alex established a different kind of record when becoming the oldest ever girl to play on a boys team with the famed Home Farm academy.