Noelle Velentzas, 28, and her former roommate, Asia Siddiqui, 31, entered not guilty pleas through their attorneys in federal court in Brooklyn.
Velentzas, in a headscarf, appeared in court smiling; Siddiqui showed no emotion. The women's next court appearance will be May 20.
Velentzas allegedly told an informant that she couldn't understand why U.S. citizens were traveling overseas to wage jihad when they could simply "make history" at home by unleashing terrorist attacks, according to a federal criminal complaint unsealed last month.
Velentzas and Siddiqui are both U.S. citizens. The charges against them include conspiracy and distribution of information about making a weapon of mass destruction.
Siddiqui had repeated contact with members of al Qaeda in the Arabian Peninsula, published jihad-themed poems in magazines affiliated with the terror group and possessed propane gas tanks along with instructions on turning them into explosive devices, according to the complaint.
Velentzas one day pulled a knife from her bra and showed Siddiqui what to do with it if attacked, the complaint said.
"Why can't we be some real bad bitches?" asked Velentzas, adding that people needed to refer to them as "citizens of the Islamic State."
Last month, Thomas Dunn, Siddiqui's attorney, told reporters, "We're going to fight it out in court."
If convicted, the women face a maximum sentence of life in prison.
In the past 18 months, the Justice Department's National Security Division has prosecuted or is prosecuting more than 30 cases of people attempting to travel abroad to join or provide support to terrorist groups. Of those cases, 18 allegedly involve support to ISIS.
In December, Velentzas and an undercover agent discussed the shooting deaths of two New York police officers
who were ambushed in Brooklyn. The shootings demonstrated how easy it is to kill a cop, she said, according to the complaint.
"Killing a police officer is easier than buying food," she is quoted as saying in the complaint, "because sometimes one has to wait in line to buy food."
When the undercover agent later pointed out that more than 25,000 officers had gathered for the funeral of one of the officers, Rafael Ramos, Velentzas complimented the agent for "coming up with an attractive potential target" for a terror attack, the complaint said.
In February, Velentzas and the undercover agent drove past a Home Depot in Queens.
Velentzas laughed about once having told a Home Depot employee that she was having a barbecue when she was looking for propane, the complaint said.
"Some women like to look at clothes," the complaint quotes her as saying. "I like to look at electric equipment."