Four car loads of Mob members then arrived at the marae.
The new arrivals stayed outside to keep watch, but the party guests began to show unrest at their presence and a fight started outside.
One of the woman's friends was punched in the face with a fist bolstered by brass knuckles. Others, including family members, were smashed in the face with a metal pole.
"At this point I was still inside drinking with lots of my family and friends while that fight had gone down, my uncle and cousin had got hit. I remember nephews and nieces and little kids were all still there," the victim said.
One of her cousins then ran into the marae screaming that the Mongel Mob were there.
The victim ran outside and in the dark saw five figures standing by a car and walked up to them thinking they were invited party guests that had just arrived, but as she got closer something didn't feel right.
"As I approached them I said 'who are you guys, this is my birthday, what are you doing here?'"
Before she finished her sentence she was punched in her right eye, bottled over the head and stabbed in the ribs, puncturing her lung.
"It pretty much just felt like automatic bruising to the right side of my body. I can't explain it, I had no idea it was a stab wound though. I fell to the ground and they carried on beating me up.
"All I can remember is just staying on the ground and I put my hands up to cover my face, I can just remember my entire body being stomped on."
As she lay on the ground a gun was fired, people poured out of the marae and the attackers disappeared into the night.
The young woman was rushed to Hawke's Bay hospital, her family by her side.
She suffered multiple head wounds, concussion, a punctured lung and broken ribs.
Her hands have only just healed from the attack as she had broken fingers, crushed nerves and tendons.
She's growing physically stronger every day as her body continues to heal, but the emotional trauma remains as raw as ever.
Three men pleaded guilty to unlawful assembly but all violence charges against them were dropped as police lacked evidence to prosecute individuals.
In November, Tama Hawkins was sentenced to 80 hours' community work and Te Rimu Hawkins was sentenced to three months' home detention earlier this week.
"Do you remember your 21st birthday Mr Hawkins? I don't ever want to remember mine," she said in a victim impact statement at Hastings District Court this week.
A third man Jeffery Morunga, will be sentenced on January 30.