One of the receipts had the word "Nah" where the tip amount is supposed to go, and the other read: "Build that wall, Trump Daddy."
Mau, who is of Filipino descent, said the teenagers apparently thought she was Mexican and were referencing President-elect Donald Trump's proposed wall at the Mexican border.
"I know they're younger, but I feel like they shouldn't treat people differently because of race," she told WTKR-TV.
Mau said the customers did not give her any indication that they had a problem with her service.
"I just can't believe people are that bold to put something like that on a credit card receipt, especially since it didn't seem like anything was wrong. If they had a problem with something I was doing or how I looked, they could've asked for someone else," Mau told WVEC-TV.
The server said she was particularly shocked the message came from young people.
"I was shocked they would even have an opinion like that being in high school. I don't think it's respectful to write that about anybody at all," she said.
Mau said she learned something from the unpleasant experience.
"I feel sorry for people who do experience this. I now know how they feel, and that's why I want to spread the word on why you shouldn't treat people like that," Mau said.