Grandparents and Third Parties: How to Get Custody of a Grandchild in Another State

I live in Greensboro NC. I have a 16yr granddaughter who lives in Philadelphia Penna. My granddaughter lives with her other paternal grandmother (mother) who pack her bags and put her out 10/2/2016210PM, because she had reefer and she could smell it. Granddaughter went to a girlfriend house and contact me this morning. Granddaughter mother lives in Philadelphia but does not get along with daughter. Father lives here with me and wants to go get her and bring her to Greensboro. NEITHER PARENT HAS CUSTODY. What rights do we have? Who do we contact to bring her here. Is she consider old enough to make a decision to come with her father without consent from mother/grandmother. Want to do the right thing to avoid anymore issues
Granddaughter does go to school and B/C average. She is not perfect an average teenager who is smelling herself which I know the hormone is working.

Grandparents and Third Parties: How to Get Custody of a Grandchild in Another State