THE mum of a McDonald's worker filmed battering a rude customer has said the girl deserved the savage beating.

Erika Chavolla, 24, was filmed slamming Sabrinah Fontelar's head against a table after she apparently insulted her mother and threw a milkshake at a Las Vegas branch last week.

Speaking for the first time since the brutal video went viral, Erika's mother Ana said: "What was she supposed to do, nothing?"

Ana, from Las Vegas, Nevada, told DailyMail.com people have always picked fights with her daughter because of her size.

The 48-year-old added: "The customer was looking for a fight. She was pushing.

"Erika doesn’t know her, she’s just a customer she comes in throwing things. What did she expect?"

Fontelar, also 24, posted a link to a news article and a screengrab of the footage on her Instagram account, with the comment: "Fat b***h".

It has since been reported that Fontelar was charged with battery while Chavolla kept her job.

She showed off the cuts and grazes she got from "hitting her in the teeth" in a new Facebook video.

Chavolla said: "She was talking a lot of 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.

"Don't talk about my momma!" she added, referencing her angry words in the original fight footage.

McDonald's is understood to be investigating the brawl and said it does not "condone the behaviour depicted in this video".

The fight is believed to have broken out when Fontelar ignored the waitress by going to fill her cup with free soft drinks.

The waitress grabs the woman, wearing just a small black tank top and grey shorts, and starts pounding her head on a table.

She throws the customer around so brutally that one of her breasts falls out of her top.

The larger woman then pummels her face with wild, swinging blows before tossing her on to a cushioned seat.

At this point, other employees try to get between the two women as the very one-sided fight rages on.

Another employee, wearing a blue shirt, eventually restrains the battered patron but gets an elbow in the face for her effort.

The first waitress tells her: "My momma ain't dead, you respect my momma."

The video was uploaded to Instagram by another customer who wrote: "So this happened at McDonald's.

"The lady asked for a water cup and supervisor shut down the soda machine because she wasn’t letting her get a free soda."

In a last-ditch effort, the customer picks up a chair but the waitress disarms her with ease.