But the 18-year-old told HLN's Ashleigh Banfield she loves the woman now sitting in jail and still considers her mom.
"I still feel the same way about her," Manigo said in an interview that aired Wednesday. "My feelings toward my mother will never change."
A DNA test revealed last week that Manigo was the infant who police said was stolen from a Jacksonville hospital in July 1998 by a woman posing as a nurse.
That woman, police say, was Gloria Williams, 51, now held on charges of kidnapping and interfering with custody. She was extradited from South Carolina to Jacksonville this week and is awaiting trial with bail set at $500,000.
Manigo's dismay has been apparent for days. Shortly after Williams' arrest last week, the teen wept and hugged her inside a jail in Walterboro, South Carolina, video shows.
"I'll probably cry more than I have in the past," she told HLN. "I just couldn't take that she was in cuffs. She's not an animal... I don't think she deserves to be in cuffs."
Manigo declined to answer questions about when she began to suspect something was amiss. But court documents reveal Manigo may have known about her hidden past for months.
Following up on a tip given to the National Center for Missing & Exploited Children
in August, detectives interviewed a witness who said Manigo claimed a year and a half ago she was kidnapped from a Jacksonville hospital as a baby, according to the affidavit for Williams' arrest.
The DNA test came during the probe sparked by the tip.
Jacksonville Sheriff Mike Williams has said Manigo "had an inclination beginning a couple of months ago" that she may have been abducted. She had discovered she had a fraudulent Social Security card and birth certificate when she began looking for jobs, the sheriff said.
She is working with an attorney to establish a valid birth certificate and Social Security number. Her birth name is just one of the shocks she is working through -- news media referred to her as Kamiyah Mobley when reporting the story last week.
She used Manigo -- the name she grew up with -- in an interview that aired Wednesday on ABC's "Good Morning America."
"Your whole life you've been known as Alexis, Lexi. Now it's like, people are referring to you as someone else, nationally," she told "GMA."
'I was given the best life'
Manigo acknowledged Williams made a mistake, but says she forgives her.
"From that one mistake, I was given the best life. I was. I had everything I ever needed, wanted, I had love, especially," she told "GMA" of growing up in Walterboro, some 175 miles north of Jacksonville.
"You can't just say, 'Oh, they did something wrong, let me just forget about them and move on.' It's not that easy," she told ABC.
"I understand what she did was wrong, but just don't lock her up and throw away the key, like everything she did was just awful. She loved me for 18 years. She cared for me for 18 years."
Nationally publicized kidnapping
Authorities say last week's DNA results ended an 18-year mystery that started with a kidnapping -- one that left Manigo's biological relatives in years of grief.
On July 10, 1998, a kidnapper, dressed as a nurse in a blue smock with flowers and surgical gloves, was captured in a grainy surveillance video at the Jacksonville hospital where Kamiyah Mobley was born, police said.
The baby's mother, Shanara Mobley, then 16, told investigators that a woman she thought was a nurse entered her hospital room and took the infant.
"Please bring my baby back," Shanara Mobley cried during an interview with CNN affiliate WJXT-TV at the time. "If you were faking a pregnancy or you just can't have no kids, how do you think I feel? ... That's my first child."
The kidnapping made national headlines. The mother eventually was awarded $1.5 million after settling a lawsuit against the medical center, WJXT reported. She has since had three other children.
Police said Williams kidnapped the baby and raised her in South Carolina. Manigo derives her last name from Williams' former husband, Charles Manigo, who was incarcerated when the baby arrived, his family has said.
But authorities said Williams also used fraudulent documents to establish the child's identity. A check of her Social Security number reveals it was issued to a Virginia male who died in 1983, court documents say.
A sample of Manigo's DNA taken at the time of her birth in Florida was matched Thursday with a swab taken from the young woman last week.
Reunited with biological parents
Manigo met her biological parents Saturday in Walterboro, WJXT reported.
Her biological father, Craig Aiken, said he told his daughter he loves her.
"The first meeting was beautiful," Aiken told the station. "It's a feeling that you can't explain."
Manigo likened the experience to meeting distant relatives. She told HLN she could envision having a relationship with her biological parents but had no idea how it could play out.
"I don't want to be like a little kid hoping everyone is going to get along," she said. What does Manigo want, then? "Peace."
Asked whether she thought about what her life would have been like in Florida, she told "GMA," "I'm not saying that they weren't going to be good parents. I'm not saying that at all. But it would have been a different life."