If she's threatening to harm herself you need to call the cops and let them deal with it. Consciously avoiding prenatal care is neglect.

She needs to see a doctor!! She's probably close to 35-40weeks!!!!!

For the safety of your niece or nephew, I would call child protective services again and report her, and tell them she knows she is pregnant and is refusing prenatal care & continuing to use drugs. I would not protect an adult willingly making these choices over an innocent child who will likely need emergency care at birth, and may have permanent damage. It's not fair to the child and your sister-in-law may get a check every month for a child she knowingly disabled. That's horrible. I wouldn't be able to live with myself. 

She's gonna kill it. I swear who does that!!!!! She better get her ass in hospital or doctor. She don't deserve be a mother. 

I agree with others:  it's time to get the authorities involved.  She's clearly not willing or capable of making the correct decision regarding this child.  I'm sorry that you've been put in this position.

The baby kicks really hard and youCan see it move in her stomache the heart beat is pretty much at her belly button at this point if that helps..