Kamiyah Mobley was allegedly abducted by Gloria Williams, 51, just hours after she was born in 1998.
Williams then convinced former boyfriend Charles Manigo that Kamiyah was their biological daughter and they named her Alexis.
But the lie was exposed after 18 years thanks to a series of tip-offs and Williams has now been charged with kidnap.
Kamiyah has since been reunited with her biological parents, Shanara Mobley and Craig Aiken.
But the man who spent 18 years raising Kamiyah as his own daughter by the name of Alexis today spoke of his heartache.
He told ABC : "One of the hardest things she said on Friday was, 'dad, I love you', even though she knows what's going on.
"I talk to her every day.
The attention is overwhelming to her. She's still processing everything.
"It's a shock to me, it's a bigger shock to her."
He continued: "She's still my child. I understand what's going on, but she's still my child."
When Williams appeared in court last week, she blew a kiss to the teenager who was in the public gallery .
Kamiyah responded by shouting: "I love you mom."
Mr Aitken previously said he spent every year on his daughter's birthday imagining "how it would be if she were here" and "what we would do if she came came back"
The girl's biological mum later sued the hospital – now called UF Health-Jacksonville but known as University Medical Center in 1998 – and received a £1.23 million ¬settlement.
It is not known if Kamiyah now plans to live with her biological family.