Amanda Bowden, of East Haven, has been charged with one count of false information and hoaxes for the threat, The Hartford (Conn.) Courant reported.
The criminal complaint against her alleges that between Feb. 6 and 14, Bowden told a friend that she was planning a suicidal bombing and mass shooting at Gateway, although she has no links to the school. She later talked with an undercover agent.
During an unrecorded conversation with the agent, Bowden allegedly spoke of the Sandy Hooks shooting and praised shooter Adam Lanza, the complaint states.
"In this day and age, the making of any threat will not and cannot be tolerated," Kimberly K. Mertz, the FBI special agent in charge, said in a statement. "There will be consequences."
Bowden appeared before a U.S. judge on Wednesday and is being held in custody until a hearing on March 1, the U.S. Attorney said.
If convicted of the charges against her, she faces up to five years in prison and a fine of up to $250,000.