Two young men who were travelling in the car were also seriously injured in yesterday's accident which happened at Cloonturk on the Kilkelly to Knock Road in Co Mayo.
The three victims were rushed to Mayo General Hospital in Castlebar. The girl was transferred to Dublin for emergency treatment.
It followed a single car crash yesterday shortly before 4pm in which a 42-year-man was killed on the Tullow to Castledermot Road in Co Carlow.
The man was pronounced dead at the scene.
Meanwhile, a 29-year-old man was killed on Saturday in a single vehicle crash in Granagh, Co Limerick.
The collision occurred at 3.55am on the Croom to Granagh road at Kilmore.
Gardai have appealed for witnesses.