A young Sydney mother who watched a woman collapse and stayed by her side until an ambulance arrived says she was 'horrified' by the encounter.

Mel Gabbusch, 32, who was at Sydney's Olympic Park district to take her daughter to a Taylor Swift concert, said she saw a young woman who appeared to be struggling to walk along the street.

'We saw her walking.. then we noticed she sat down, pretty much collapsed into a chair,' Ms Gabbusch told Daily Mail Australia.

A young Sydney mother posted a picture to social media after she helped a woman outside the Stereosonic music festival

'She clearly wasn't well and her friends asked for some water. We kept watching and she passed out"

The 32-year-old said she helped the young woman until the ambulance arrived.

'I got her on the ground and put her on her back, meanwhile all her friends were arguing over who was going to ride in the ambulance with her, because none of them wanted to miss Stereosonic,' Ms Gabbush said.

'It was terrible. I turned around and said to them they should be more worried about saving their friend and less about a stupid concert.

One woman has died, and another is in an induced coma after attending the Stereosonic music festival in Sydney on Saturday

A group of festival-goers pose for a photo during Stereosonic in Sydney on Saturday

'It was very scary - I have a son who turns 15 in a few weeks, I sent him a message and the photo straight away and told him to show his friends and tell them what happened.

'It still makes me really angry, I'm a parent so it really gets to me and is a scary situation.

'I was trying to stay calm, but it's terrifying how bad this could have been.'

Dozens of revellers have also been charged with possessing and supplying drugs at the festival

A young woman wearing cut-off shorts and a singlet strolls through the crowd at Olympic Park in Sydney

It comes after one woman died and another was in an induced coma after the dance festival on Saturday.

A 25-year-old woman fell ill during the event and was rushed to the Concord Hospital, where she later died.

A 22-year-old woman was taken to Westmead Hospital was previously in a critical condition and was placed in an induced coma. On Sunday morning her condition was upgraded to 'stable'.

The festival organisers released a statement following the tragic news, urging people to 'stay safe and look out for each other'.

Swedish duo Galantis entertain the crowd of people at Stereosonic in Sydney on Saturday

'Totem Onelove conveys our deepest condolences to the friends and family of the patron who tragically passed away on Saturday night at Sydney Stereosonic. As it is a matter with the NSW Police and Coroner we cannot make any further statements or comment,' the statement read.

At least 69 people have already been charged with possessing and supplying drugs at the festival, while 23 others were issued with 'cannabis cautions', according to NSW Police.

More than 48,000 people packed into the Sydney Showgrounds for the 11-hour event.

More than 48,000 people packed into the Sydney Showgrounds for the 11-hour event

Assistant Commissioner Frank Mennilli said police were disappointed by the behaviour of many people at the festival.

'The police operation is about minimising harm and providing a safe and secure environment for revellers to have a good time,' he said.

'The operation is still underway, and we already have 69 people charged for drug possession and supply.

'This number is alarming and disappointing, especially after we warned revellers about the dangers of drug use.'