She is accused of sending thousands of dollars to the so-called Islamic State group in Syria through a Western Union money transfer, reports say.
The girl and a male accomplice, 20, who allegedly gave her the money were arrested in raids on Tuesday.
The pair allegedly met in a park on Tuesday to discuss a plan to send money to Syria that day, reports said.
They had reportedly developed a "sophisticated facilitation path" of wiring funds and had completed successful transfers before.
The man, named by media as Milad Atai, was also arrested during Australia's biggest counter-terror raids in September 2014.
The girl is accused of admitting to a police informant that she had wired A$10,000 ($7,600, Â£5,400) to Syria at the behest of an Islamic State fighter.
She was also allegedly planning to conduct another transfer of A$5,000 when she was caught on Tuesday morning in a park along with Mr Atai, who had handed her the money.
But her lawyer argued that the prosecution's case was based on inferences in her conversations with the police informant and said it may have amounted to entrapment.
Mr Atai faces charges similar to the girl's.
The Australian Broadcasting Corporation said Mr Atai was still under investigation over the death of police accountant Curtis Cheng, who was gunned down by 15-year-old Farhad Jabar.
Police have reiterated concerns over extremists targeting young Australians.
"[It is] disturbing that we continue to deal with teenage children in this environment," NSW Police Deputy Commissioner Catherine Burn told reporters on Tuesday.
A Sydney girl, 16, has appeared in court on terror financing charges which carry a maximum term of 25 years' jail.