Harboring a fugitive refers to the crime of knowingly hiding a wanted criminal from the authorities. Federal and state laws, which vary by state, govern the crime of harboring a fugitive
You could be in serious trouble if you harbor a runaway. If your niece ran away because of a dangerous situation, then call the police and report her presence as well as the situation. She should not be return to that situation but the state needs to know where she is. Perhaps you could seek her guardianship. "No active parents" is a vague term. Have the parents' rights been terminated? Many facts are missing. A critical fact is the reason your niece is a ward of the state.
Harboring a Fugitive.
The author provides the preceding information as a service to the public. Author's response, as stated above, should not be considered legal advice. An initial attorney-client conference, based upon review of all relevant facts/documents, will be necessary to provide legal advice upon which the client should then rely.