Sarenna Forno, from Oak Flats, pleaded guilty to assault occasioning actual bodily harm in Wollongong Local Court this week in a plea deal with police that saw a more serious charge of recklessly causing grievous bodily harm dropped.

Court documents said the 21-year-old was out in the CBD with a group of friends, including the victim, an American in Australia on a working visa, on the evening of March 9 but became so intoxicated she was kicked out of the Grand Hotel twice about 1.30 the next morning.

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Meanwhile, the victim and the others in the group decided it was time to leave and planned to catch the 2.30am train to Dapto.

Forno became angry her friends were leaving and confronted one of the group, upsetting the other girl.

The victim tried to speak to Forno, however the exchange became heated and pair began pushing each other.

Forno then punched the victim in the mouth, causing her tooth to fall out into her hand.

The victim stood up and hit Forno back in a bid to protect herself, however Forno continued punching the victim in the face.

Another girl in the group separated the pair.

Court documents said blood was gushing out of the victim's mouth and she could feel her teeth were dislodged.

She was taken to Wollongong Hospital where it was revealed one tooth had been completely knocked out, two more were only hanging by a thread and two more were fractured.

Her gums were also badly traumatised.

Doctors set the teeth with a splint however the woman will require ongoing treatment. She has since returned to her home in the US.

Forno was arrested on March 24. When interviewed, she admitted to throwing the punch but claimed she retaliated to the victim pushing her.

Forno will face sentencing on December 17.