Tierra Payton says she didn't know the bill, which she said was given to her by her aunt, was fake.
"I don't have a money marker to determine. It's not that I knew. I'm more surprised than they are," she told WSB-TV, Atlanta, Tuesday.
Once Dutchtown High School officials determined the bill was fake, the junior was suspended pending a Wednesday hearing. Payton faces expulsion and deferment to an alternative school.
"I don't think anyone, I don't care who it is, should be made to feel like they're a criminal before any trial or anything has gone on," Payton's aunt Cheryl Gardner said.
"And I shouldn't miss almost a week out of school because of something like this," Payton said.
Gardner said she got the bill from a self-checkout machine at a home improvement store.