What the DOJ press release and FBI materials confirm is this sequence:
FBI agents interviewed Carlina — now identified — and gathered her account. Pettway, by this time, had been living in Raleigh, North Carolina, where she was on probation for a conviction of attempted embezzlement in that state. On January 23, 2011, Annugetta Pettway surrendered to authorities. She was arrested in Bridgeport, Connecticut, and on the same day FBI Agent Maria Johnson conducted an interview in which Pettway admitted what she had done.
Pettway told the FBI that she had suffered several miscarriages before going to Harlem Hospital in 1987. She said she took the infant from a crib and brought her to Bridgeport by train. She admitted she had no documents for the child. She admitted she had attempted, at some point, to create a forged birth certificate. She said she was sorry and that she knew she had caused a great deal of pain.
On January 24, 2011, Pettway was charged in Manhattan federal court with one count of federal kidnapping. The criminal complaint was filed by the U.S. Attorney’s Office for the Southern District of New York, then headed by Preet Bharara.
Federal charges were necessary in part because New York State’s statute of limitations may have expired for the relevant state-level charges. Federal kidnapping law, however, carries no statute of limitations when the victim was under eighteen at the time of the offense and is still alive. The offense was federal from the start — taking a child across state lines, from New York to Connecticut — and federal jurisdiction allowed charges to proceed regardless of how much time had passed.