They'll face Shelbourne next month.
Athlone Town are into their their fifth consecutive Women's FAI Cup final following their victory over Galway United on Saturday.
Lily Agg's side needed penalties to secure victory following a 1-1 draw after extra time.
Alexis Strickland put Athlone ahead after nine minutes, but Galway responded strongly, with Cara Griffin scoring a spectacular equaliser in the second half.
The penalty shootout was level after the opening four kicks, before Isabella Beletic missed for Galway, with Roisin Molloy converting for Town and Matthaiou then saved Niamh Farrelly's penalty to send Athlone through.
They'll now face Shelbourne for the fourth time in the decider next month.
Full Interview: Portarlington Footballer Ronan Coffey
Full Interview: The Down's Manager Dermot Power
St Brigid's And St Joseph's Aiming To Reach Leinster Semi-Finals
Ballinagar And Milltown To Meet In Leinster Intermediate Quarter-Final
Ronan Coffey Praises Portarlington’s Young Guns Ahead Of Leinster Quarter-Final
Mauricio Pochettino Set To Be Appointed Manchester United Manager
Darragh Murray Named In Irish Squad For Fiji Clash
Portlaoise Panthers Aiming To Bounce Back In Division One
Portarlington On The Road In Leinster
The Down's Building Towards Leinster Football Quarter-Final
Laois Provisional League Fixtures Revealed
The Harps Manager Praises His Sides Efforts In Leinster
Buccaneers Claim Back To Back AIL Wins
Kilcormac Killoughey Captain Full Of Praise For Goalkeeper
Lough Lene Gaels Suffer Late Heartbreak In Leinster Quarter-Final
Crookedwood Win Leinster Junior Camogie Title
Conor Slevin Wins Dramatic Leinster Quarter-Final For Kilcormac Killoughey
Ireland Secure Comfortable Win Over Argentina
Kilcormac Killoughey Seal Win But Heartbreak For Lough Lene Gaels And The Harps