Administrative rights on another device

My friend has been having problems with her phone the last couple of weeks. She got someone to check it out and I have administrative rights for her phone. It supposedly originated from my phone but dont have the skill or know how to do it. I would like to know if anyone else has had this issue. She is frustrated because she cant access any of her phones features and I'm frustrated because I dont know how to help her. I need to know how and why this person was able to do this...