Agree with what Buzzkill and Rachael said. Are you able to take her on yourself?
At the least, do your homework, and find out what "safe houses" are in her area, and give her the immediate directions to the facility, or drive her yourself, until something can be worked out with her immediate family (mom).
I know from my experience, that reacting to my son's behavior, instead of calmly responding, was the wrong thing, and therefore, I made the wrong decision, the biggest one I have ever made. Don't let that happen to your neice, if at all possible.