Fatima Elomar, 31, was intercepted at Sydney Airport in May last year as she tried to board an international flight.
Cash, camouflage gear and medical supplies were found in her luggage.
In a brief court appearance, she pleaded guilty to supporting incursions into a foreign state with the intention of engaging in hostile activities.
Mohamed Elomar travelled to Syria and then Iraq in 2013 to fight with so-called Islamic State (IS).
Court documents reportedly detail text messages between the couple in which Ms Elomar begs her husband to return home for medical treatment after being shot.
Mr Elomar reportedly told his wife to prepare the children's passports so they could be together in Raqqa, Syria.
Mr Elomar, and fellow Australian Khaled Sharrouf came to public attention last year after they posted pictures of themselves posing with severed heads to social media.
One of those images showed Sharrouf's seven-year-old son holding up the severed head of a Syrian soldier.
It is believed Elomar died in June during an air strike on a convoy of vehicles near IS's self-declared capital of Raqqa.
The Australian government estimated in September that around 120 Australians were currently in Iraq and Syria to support IS and other terror groups.
The wife of one of Australia's most notorious extremists, Mohamed Elomar, has pleaded guilty to supporting overseas terrorism.