Court papers say Jessica Bowie discussed attacking the New York state Capitol on July 16, then surveilled the building through July and August before her Aug. 19 arrest.
Aug. 5 purchases at a local Home Depot included bomb materials, and prosecutors say Bowie also obtained a delivery bag and sought a gun for the attack.
An FBI-directed source posing as an ISIS facilitator messaged with Bowie online; the complaint says she learned the Capitol could hold about 200 people and hoped to kill at least half.
Prosecutors also say Bowie repeatedly created new social media accounts because platforms kept blocking them, adding to evidence they say showed persistence in pursuing the alleged plot.