The 53-year-old, who lived alone in the 24-storey block with her cat Rosie, heard a commotion outside, went to the window and quickly realised a massive fire had engulfed her building.
"People were telling me to jump," she told AFP, sipping tea at a residents' support centre ahead of the first anniversary Thursday of the tragedy that killed 71 people.
"The fire brigade officer told me to stay put. He said we'll get to you eventually.
Eventually fear forced O'Hara to defy the firefighter's advice and flee the flat.
She gathered a few belongings, distraught at the realisation she would have to leave Rosie behind.
Her last memory of her home for nearly two decades: the cat seated on her sofa looking back up at her.
O'Hara found the building's only stairwell already choked with dense smoke.
"I had to feel my way around the hallway because it was so dark, smoky and all the way down the stairs I just kept shouting 'help me!'"
Once she made it to the second floor she was met by other residents and firefighters who led her out to safety.
The London Fire Brigade's policy of telling residents to "stay put" should have been abandoned within half an hour of the blaze's outbreak, a recently-released report by a fire engineer found.
Yet it remained in place for nearly two hours.
O'Hara believes her decision to escape the burning building may have been the difference between life and death.
"I was glad that I didn't follow that advice and I just hate to think what would've happened if I'd stayed put.
"I was scared and I just knew I had to get out. I didn't want to die in there."
'Broken heart syndrome'
At the end of last year the local council, which owns Grenfell, permanently rehoused her in a brand new flat with a balcony several miles away.
O'Hara is one of only 82 households to get a new home out of 209 in need following the fire.
But without any roots in her new neighbourhood, she regularly travels back to the Grenfell area where she has spent much of her life.
"I feel like I've been displaced and that I want to come back, she said.
"It's also stressful now as it's the one-year anniversary.
"I just feel very emotional: angry, guilty for surviving, hurt -- it's all a lot of emotions mixed up in one."
O'Hara has been diagnosed with broken heart syndrome and told she will need to be on medication for the rest of her life.
Things became a little more bearable two months after the fire, when she received the most welcome of phone calls from a vet.
A microchipped cat had been brought in.
Rosie had miraculously escaped the inferno too -- with just a scratch on her face to show for it.
When they were reunited, O'Hara remembers: "I was so traumatised, emotional all over again, crying."
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)