How do I go about getting custody of my soon to be 2yr old niece?

My niece has lived a very turbulent life. At the young age of 3months she came to stay with me in VA. She lives in NC. Every since then she would spend months at a time with me only going back to her parents when she had an doctors appointments. On several occasions she came back to me with a cold, some worse than others. Her mother and father are not married and not together. They’ve been on and off since she was born. They’re very toxic around each other especially when her mother drinks. Their arguments have become violent and have since traumatized my niece. Her mother currently has a CPS case open. The mother is very unstable and can barely take care of herself. My niece has moved from home to home due to the fact her mother does not have a home of her own. She also does not have means of transportation. She’s in and out of work depending on other people. My niece has basically become my daughter. I’m her safe haven.