Helen Kelly's underwired bra deflected the bullet which doctors believe was heading towards her heart.
The narrow piece of metal wiring, which snapped under the impact of the shot, bounced the bullet away from her heart and through her right breast.
Yesterday, as two of the men involved in the shooting outside the Barbican Centre in central London were jailed, Miss Kelly, 24, an accountant from London, described the moment she was wounded. "I heard what we thought were gunshots," she said. "I did not really believe they were gunshots but I suddenly saw my friend running. I started to follow her and it was not until we got to the other side of a wall that I realised I had been hit."
The shooting happened at midnight, after the Urban Music Awards on 9 November last year.
City of London Police said the two gangs, one of which was connected to a hip-hop band from south-east London, first confronted each other in the VIP lounge.
The altercation was taken outside where around four men on one side of the road began firing shots at four men on the opposite side, as hundreds of people who had been attending the music ceremony poured out of the venue.
Miss Kelly had been on a night out with friends when she was injured. She was the only person to be hurt in the gunfire, although hundreds of people were on the street at the time.
Linton Ambursley, 29, of Lewisham, who had admitted wounding Miss Kelly, was jailed for 12 years, while Tyrone Headley, 28, of New Cross, admitted assisting an offender and was imprisoned for 30 months.
The gunman, Ambursley, fled from the scene but was arrested by police moments later, along with Headley, a former record company chief who was driving the getaway car.
Officers did not realise the two men had been at the shooting but stopped the car because its headlights were switched off.
Ambursley was wearing body armour usually worn by the British military. A third man who fled from the car was found to be an illegal immigrant and deported to Jamaica.
Detective Chief Inspector Bob Wishart, who was leading the investigation, said yesterday that Miss Kelly was "incredibly lucky" to be alive and that it had been "millimetres from a murder inquiry".
Miss Kelly, who was at the Old Bailey for the sentencing, told the London Evening Standard that she did not realise she had been seriously wounded at first.
"I didn't think I had been shot; I thought I had been hit by a ricochet, a bit of wood or something," she said. "It didn't hurt very much - you know how you cut your finger and you feel a sharp pain, that's all it was.
"We carried on running and a girl in front of us was shouting 'She's been shot, she's been shot'.
"That's when I realised I might have been shot. There was a lot of blood on my stomach but I didn't know where it was coming from. I could see where the bullet had gone in but not where it came out."
She said she was convinced she was going to die as she lay bleeding.
"I sat down and thought, 'Well, this is it. I have done all my washing so my mum won't have to go through all dirty clothes when I'm dead'."
Miss Kelly, who originally comes from Tyneside, had only been in London for four weeks when she was shot, after taking a job in the City.
Mr Wishart said the bullet was likely to have caused far worse damage had it entered her chest.
"If it had not been deflected by the underwire, it would have gone in the torso in an area with her heart and lungs," he said.
"Once the bullet enters the body, it can either splinter or change trajectory, doing a lot of damage."