The woman threatened a firearms and explosives attack of "a magnitude surpassing the March 15, 2019 Christchurch mosque massacres", causing "significant disruption" to the people of New Zealand.
Otago Polytechnic and University of Otago ceremonies scheduled for December 9 were called off, affecting thousands of graduands.
She stood with her head bowed and hands clasped together in the dock at Auckland District Court this afternoon.
Judge Ema Aitken acknowledged her guilty plea.
"It takes a lot of courage to take responsibility for your actions," she said.
The woman, in her early 20s, will be sentenced on October 28.
She is seeking discharge without conviction.
Her interim name suppression continues until sentencing.
She has been released on existing bail conditions.
