A customer threw her drink at a S.F. restaurant employee over 25 cents.

An employee was working during the lunch rush at Umai Savory Hot Dogs at the Stonestown mall in San Francisco on Friday, May 13, when an angry customer suddenly chucked her drink directly at the staff member and cursed at her.

The Umai customer was upset because the cashier mistakenly charged her for chili cheese fries instead of regular cheese fries, according to owner Dat Thieu. The cost difference: 25 cents.

The customer called the Umai employee a “b—” before walking away and yelling, “sorry, not sorry,” as seen in security camera footage gaining attention on social media. The red drink splattered onto the employee, who stops briefly to wipe her face and clothes with paper towels before returning to work. Other diners look stunned, but don’t intervene. A BIG SALE. A GREAT DEAL. 1¢/day for 6 months ACT NOW The employee left work early that day and hasn’t come back since, Thieu said. The incident speaks to an increasingly tense dynamic between overworked, short-staffed restaurants and customers eager to return to normalcy. Anecdotes about confrontations and even violence over mask mandates and aggressive diners have abounded during the pandemic. An East Bay restaurant drew attention last year after asking customers frustrated by long wait times to “not pull a ‘Karen’ and write us a bad Yelp review.” Last summer, a Massachusetts restaurant temporarily shut down for a “day of kindness” after customers made staff cry. In the Bay Area, restaurants are also getting battered by short staffing, a spike in COVID-19 cases and temporary closures as a result. It’s not the first time a customer has mistreated an Umai employee. Workers whose first language isn’t English, including this staff member, have especially become targets of irate customers, Thieu said. Since the hot dog chain opened its newest location at Stonestown six weeks ago, he’s seen at least four customers scream at employees who don’t speak English well. An employee at Umai’s Westfield location in downtown San Francisco recently quit after a similar incident. Workers have started crying and asking to leave early after negative interactions with customers. “For whatever reason, it’s to the point where they’re not human,” Thieu said. “Even (for) my employees that do speak English ... the compassion level is definitely not there anymore.” A Umai Savory Hot Dogs at Westfield San Francisco Centre in San Francisco.Scott Strazzante/The Chronicle 2021At Umai, security cameras show the cashier refunding the angry customer for the fries plus an additional item, but the customer remains agitated. She eventually leaves then comes back a few minutes later and throws her drink cup at the employee’s face. Thieu said he’s noticed customers becoming more impatient. He’s tried to ameliorate their frustration with wait times with offers of free drinks, which has only upset other customers who aren’t getting a free item. But it’s Umai’s San Francisco locations in particular where he’s seen abuse of employees who don’t speak English well — more so than at his San Jose restaurant. The San Francisco locations are fast-paced and see higher traffic, he said. The staff member who was accosted last weekend is one of his best employees, he said. She works two jobs: as a cashier at Umai during the day and as a delivery driver for DoorDash at night, he said. He’s texted her several times since the incident, including offering his support in filing a police report, but she hasn’t responded. The climate at restaurants right now is one reason it’s so hard to find employees, Thieu said. He often feels more like a therapist than a boss, talking down workers who are upset by customers’ bad behavior. Even an Instagram video of the incident — which Thieu posted in the hope of reminding people to be kind to restaurant workers — drew a complaint from a customer who said they waited half an hour for an order a few weeks ago. Another commenter who identified themselves as a former McDonald’s worker wrote: “This is one reason I’m scared of going back to working retail or food.” “That old cliche of customers are always right,” Thieu said, “isn’t necessarily always true.” Elena Kadvany is a San Francisco Chronicle staff writer. Email: elena.kadvany@sfchronicle.com Twitter: @ekadvany