So Cuevas pretended the 6-year-old girl had gum in her hair, removed five strands from the child's head, folded them in a napkin and placed them in a plastic bag.
"Because of TV, I knew they needed hair for the DNA," Cuevas said Tuesday.
The DNA tests confirmed a mother's intuition.
The girl was Cuevas' only daughter, Delimar Vera — the girl everyone else believed had perished in a house fire when she was only 10 days old.
Investigators believe a family acquaintance stole the baby from her crib, set the fire to cover the crime and raised the little girl as her own.
Carolyn Correa, of Willingboro, N.J., who was wanted on charges of arson and kidnapping surrendered to police in Philadelphia Tuesday afternoon, said her attorney, Jeffrey Zucker.
The little girl has been taken into state custody in New Jersey. It was not immediately clear when she would be reunited with her mother.
Fire officials believed the 1997 blaze at Cuevas' Philadelphia home was sparked by a home-rigged extension cord connected to a space heater. The fire was put out in 10 minutes, but Delimar's room was gutted, and investigators concluded that the infant's body must have been consumed by the intense heat and flames.
Cuevas said several things made her suspicious.
"I went inside the room and looked in the crib and she wasn't there," Cuevas said, adding that the window was inexplicably open though it was a cold winter evening. Police and fire officials that night told the hysterical mother that "maybe it was my nerves."
Cuevas, 31, said she was also suspicious because Correa, 42, had announced that she was pregnant during a visit shortly after Delimar's birth. According to Cuevas, Correa abruptly ceased contact after the blaze.
Cuevas, who speaks in halting English, said she instantly recognized the child as her daughter at the Jan. 24 birthday party. It was unclear what brought the girl, who was being called Aliyah, and her biological mother to the same party.
"When I see her, I saw that she was my daughter," said Cuevas. "I want to hug her. I want to run with her."
"I feel so happy, you know, that I found my daughter," Cuevas told reporter Walt Hunter of CBS affiliate KYW. "One day, she'll call me mommy. You know. She'll say 'You are my mommy.'"
She sought help from state Rep. Angel Cruz, who represents the poor, largely Hispanic neighborhood where Cuevas lives. Cruz said he was skeptical at first but "something inside" told him that there could be something to the bizarre claim. He called police, who contacted Correa for a DNA test that ultimately proved Cuevas right.
"It's a mother's way. It's motherly intuition," the lawmaker said.
Cuevas and Delimar's father, Pedro Vera, 39, had a baby boy after Delimar's disappearance but broke up under the strain of losing their daughter.
"Right now I want to see my daughter," Pedro Vera said. "I am so happy. I just want to see my daughter."
It will be up to a Family Court judge to determine where the little girl will live.
Correa pleaded guilty to a 1996 arson at a medical office in New Jersey and got five years' probation, according to court records.
Neighbors who used garden hoses and fire extinguishers in a futile attempt to help Cuevas reach her newborn on the night of the fire reacted to the news with joy and anger.
Jose Rosario, a former next-door neighbor, said he took a drink to celebrate.
"I was happy she was alive," said Rosario, who recalled grabbing a fire extinguisher and desperately trying to enter the window where Delimar was supposed to have been, only to be repelled by the intense flames.
"Somebody could have got hurt trying to save someone who wasn't in there," Rosario said. "The way she hurt those people, she should be put away in a crazy house."