The child im watching stole my boyfriends jeep? (14y/o)?

basically i watching this teenage brat till her mother gets out of jail she does not have a father her mother is in jail for cooking up meth with her boyfriend .. I'm trying my best to give her child a better life then her mother ever possibly could! She was doing fine as i thought until i found out she was with my best guy friend he is 23y/o a year older than me! He struggles with drug problems himself! Well last night she stole my best friends jeep and went god knows where and took a case of beer and Jagger from my house .. didn't come home till i had to go to work .. I got her piss tested and she came up everything possible! I don't even know if i can help her i feel like ripping my hair out!