A school girl has been left “quite shaken” and with a small graze to her leg after she was allegedly robbed and dragged inside a western Sydney police station by a woman with a knife to her throat.

The 16-year-old was waiting outside Bass Hill police station just before 4pm yesterday when her alleged attacker, 18-year-old Kylie Balawagaga, approached her, armed with a knife.

“She has demanded property from the young girl, and has held that knife against her throat,” Superintendent Bradley Thorne told reporters today.

“The young girl has handed over her phone before both have fallen to the ground. When she got back up, the woman has held that knife against her throat against and walked her into Bass Hill station.”

The young girl and the woman are not known to each other.

A senior constable on duty began negotiating with the woman to drop the knife, and let her victim go.

After she was ordered to drop the knife, the teenager courageously flicked it away, allowing the officer to make an arrest.

The victim's parents were too distraught to speak on camera, but over the phone, they said they were proud of their daughter's bravery and composure. 

“Things pop up (every day) that are completely unexpected … It is concerning anytime someone is armed with a knife, or any other weapon," Supt Thorne said. 

The woman appeared at Burwood Local Court today charged with several offences including armed robbery, kidnapping and assault occasioning actual bodily harm.

A magistrate was told the 18-year-old has serious mental health issues and was coming off the drug ice when she allegedly carried out the rampage. 

She will spend at least eight weeks behind bars and will next face court in April. 

With 9NEWS reporter Tiffiny Genders.

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