Ana O'Brien, the daughter of trainer Aidan, was reported to be conscious when taken to hospital by air ambulance after a fall at Killarney on Tuesday evening.
O'Brien, 21, was quickly attended to after her mount Druids Cross, trained by her brother, Joseph, slipped up over two furlongs out in the Celtic Steps The Show At Killarney Racecourse Rated Race, the second contest on the card which was run at 6.20pm.
The three-year-old Druids Cross was fatally injured, while O'Brien was taken off the track in an ambulance before being transferred to hospital in Cork, the Irish Coast Guard air ambulance arriving at 7.45pm and landing on the golf course in the middle of the circuit.
The third race was delayed for well over an hour as a result, although the meeting was completed, with the last race run at around 9.20pm.
O'Brien rode in both the English and Irish Derbys for her father this season and partnered her first winner as a 16-year-old at Dundalk in February, 2013.
Clerk of the course Val O'Connell said: "She was conscious leaving the track and was airlifted to Cork University Hospital."
Champion jockey Ruby Walsh, who claimed the final event on 7-4 favourite Conrad Hastings, earlier told At The Races after supervising the win of the Willie Mullins-trained Grainne's Dream in the delayed 6.50: "I think the news was a bit better when she was leaving, so hopefully that is right.
"She'll be well looked after, fingers crossed for her."