Sonya Thomas, who is all of 5 feet tall and 105 pounds, gobbled down 181 chicken wings to Chestnut's 169 and won the ninth annual National Buffalo Wing Festival.
Chestnut was favored to win but had to be satisfied with second after eating the 4.55 pounds of chicken wings.
This was the first time the two met face to face.
"They pushed each other really hard," the found of the festival Drew Cerza told the Associated Press. "Joey is so strong. He's got great jaw strength. But Sonya's so fast with the hand," he added.
Thomas may continue to give Chestnut a run for his competitive-eating money. She's already set eating records for oysters, hard-boiled eggs, cheesecake and jalapeno peppers in the past few years.
The sprightly 43-year-old said she owed Sunday's triumph to her fancy finger work.
"Sometimes if I try to chew too much I slow down," she said. "I used my hands more than the mouth."
During the public contest, in front of thousands of people, she twirled the wings in her small fingers while quickly tearing off the meat with her teeth and lips.
Her cheeks were covered in a sheen of orange Buffalo sauce by the end.
But she said she was still hungry afterward, calling the wings "an appetizer." About an hour later, she made a guest appearance in the Ridiculously Hot Buffalo Wing Eating Contest and ate 20 more.
"The hottest wings!" she said. "I had to drink a lot of water."