A McDonald's employee and the customer she body slammed after the patron threw a milkshake at her, hit her in the face with a metal tray and insulted her mother, have been identified.

Erika Chavolla, 24, was working at a Las Vegas McDonalds when she got into a dispute with the 24-year-old customer after she allegedly tried to fill up a water cup with free soda.

Sabrinah Fontelar, of Las Vegas, has since bragged on Instagram that she was the customer in the video and has posted screen grabs from the shocking video and links to DailyMail.com's original story.

Erika Chavolla (right) was working at a Las Vegas McDonalds when she got into a dispute with Sabrinah Fontelar (left) after she allegedly tried to fill up a water cup with free soda.

The two women got into a heated fight in McDonald's. The employee can be seen body-slamming Fontelar

She has claimed on social media she was charged with battery over the incident.

Chavolla said on Thursday that she has kept her job at McDonald's following the incident.

She also showed off a scratch on her hand, from where she 'hit her in the teeth.'

'It's crazy, people think just 'cause you're working...' she said in a video posted on Thursday. 'She was trying to smack for a long time.

'I wasn't even going to hit her. When there's a big girl coming towards her, she started freaking out.

'Dont talk about my momma!' she added, laughing.

Sabrinah Fontelar, of Las Vegas, has since bragged on Instagram that she was the customer in the video

The customer, who self identified as Fontelar, can also be heard saying 'that's why your a** is behind the f***ing counter' before throwing a French fry across the restaurant

Chavolla (left and right) said on Thursday that she has kept her job at McDonald's following the incident

Chavolla said she was stunned the video had become such a viral hit.

'That s**t was crazy, it went everywhere,' she said, adding that she had also seen some of the negative comments about her size. 'I seen all the mean stuff they posting.'

McDonald's said it is investigating the incident and 'do not condone the behavior depicted in this video.'

DailyMail.com reached out to Las Vegas police for more details.

Witness Marie Dayag, who posted the viral video and follow up with Chavolla, said the row between the two women started when the customer tried to put soda in a free water cup.

Dayag wrote: 'The lady asked for a water cup and supervisor shut down the soda machine because she wasn't letting her get a free soda.'

Dayag's video shows the two women arguing before the fight breaks out.

While the audio is difficult to hear, the row appears to be over money. Chavolla can be heard saying 'since you can't afford one'.

The customer can also be heard saying 'that's why your a** is behind the f***ing counter' before throwing a French fry across the restaurant.

She can also be heard repeatedly shouting 'fight me' across the restaurant.

A second piece of footage shows the fight breaking out after Fontelar hurls a milkshake at the employee.

As Chavolla storms toward her, she picks up a metal tray and hits the employee in the head with it, but she barely notices.

Instead, the worker grabs the customer by the hair and begins raining punches down on her head and face.

A McDonald's worker was filmed brutally beating a customer somewhere in the US after the female patron threw a milkshake at her (left) and hit her with a tray (right)

Chavolla then picks her up and throws her over a nearby table as other employees and even a customer run over to try and break it up.

The pair are eventually separated as another McDonald's worker tries to move the customer away, but Fontelar then begins fighting her instead.

That restarts the brawl, with the customer beaten in the head and face a second time before Chavolla throws her over another table.

At one point Chavolla can be heard shouting 'my momma aint dead, you respect my momma!'

The customer also picks up a chair and makes as if she is about to hit the employee, but is quickly disarmed having apparently given up all hope of winning.

A few more angry words are exchanged but no more punches are thrown before the footage cut out.

The employee rains blows down on the woman's face and head before body-slamming her into a table as other staff members and a customer try to intervene