With 15 attempts on goal, 37 crosses and 10 corners taken, Ireland applied as much pressure as they could on the Albanian goal in search of a breakthrough that eventually came on 88 minutes.
Up to that point, it was unclear whether this game would be completed such was the torrent of heavy rain that poured down on the pitch in the Loro Borici Stadium. Play was suspended for 60 minutes for the pitch to be drained.
Ireland, naturally, struggled to get their patterns of play together in the first half but found their flow in the second period with some fresh introductions helping to add width and speed to their play.
The impact of Izzy Atkinson on the left flank gave Ireland a new outlet as captain Katie McCabe pushed further forward to support Kyra Carusa, who held the line well.
It was Carusa who eventually pulled the ball back inside the penalty area for O'Sullivan to fire in from close range. It wasn't the prettiest goal but it was hugely important to seal the win.
The victory made it four in a row for Ireland, who secured promotion to League A due to Northern Ireland drawing with Hungary in the other game in Group B1.
Albania: Rexhepi; Gjini, Maliqi, G Berisha, Hila; Krasniqi, Franja, Hamidi (Metalla 63); Doci, Maksuti (Troka 86), Tukaj.
Ireland: Courtney Brosnan; Abbie Larkin (Izzy Atkinson 63), Caitlin Hayes, Louise Quinn, Diane Caldwell, Katie McCabe, Erin McLaughlin (Heather Payne 46); Tyler Toland, Sinead Farrelly (Jamie Finn 46), Denise O’Sullivan; Kyra Carusa.
Referee: Araksya Saribekyan (Armenia).