She is now restricted to communicating through blinking her eyelids and has no other movement in her body. She has spent the past five years receiving treatment in hospital.
The young woman, from Carrigaline, Co Cork, suffered two devastating strokes during surgery in February 2008 to remove a non-malignant brain tumour.
The tumour was detected after Catherine, who has a 12-year old son called Brandon, complained of difficulty in swallowing, repeated headaches and dizziness.
The strokes left Catherine a prisoner in her own body and she has been cared for over the past five years by Cork University Hospital (CUH) staff and her parents, Pat and Margaret.
Pat revealed a major fundraising campaign has now allowed their home to be adapted sufficiently to allow Catherine to be cared for there.
The family will discover today if Catherine will be allowed home for just two hours on Christmas Day before being returned to care in a special step-down facility.
"We don't know what is happening yet. We will find out later today but we are praying Catherine will be home on Christmas Day and home for longer in the New Year," he told the Herald.
"Catherine is very stable now and is not getting any worse. In fact she has become a bit better."
The O'Learys have spent over €50,000 on adapting their home to Catherine's unique needs with the construction of an extension, a special wet room, a ceiling-mounted hoist and wheelchair accessible rooms.
"The house has had to be turned into a mini-hospital and we are now trying to sort out the nursing care issue," he said.
Mr O'Leary gave up his job to look after his daughter and said he is convinced that a return to the familiar surroundings of her home will benefit her after so long in hospital.
Catherine was flown to England for specialist care in 2008 but suffered a serious worsening in her condition and almost died.
She has been back in CUH for three years and requires round-the-clock care.
Her family has had special meetings with HSE officials since October over Catherine's planned move back home.
Details of Catherine's story and her fundraising appeal are available from www.catherineoleary.com.