Exactly what can I do if I witness or overhear violence that is physical threats?
If you think there was immediate real risk and therefore she and her kiddies are planning to be harmed, phone the police on 000 instantly.
At another time, ask about whether or not she would like you to call the police if you do have the opportunity to talk to her. She might worry that calling law enforcement will make things even worse on her behalf. People fear so much relating to the authorities, specially those from non-English speaking backgrounds or native communities whom could have had bad past experiences.