I need advice from actual teachers

I'm not a teacher but have taken a long term sub position. For 4th grade. There's this girl who I was a summer camp counselor for and she's in my class and I'm not ready for it or her mom. It's not even that her mom is a passive parent. She's actually kind of strict but she will advocate for her daughter is she feels her daughter is being wronged. Which is good. The problem is this little girl is so manipulative. She will make tears come out of her eyes when telling a blatant lie. Even on her mom. She claimed her mom was going to beat her and our coordinator told her to stop it and stop being dramatic . And before anyone says it if it was any other kid our coordinator would not have said that but this girl will and manipulate to get out of trouble. They had to call CPS last summer because she said we couldn't tell her parents that she busted a kids head open because her step dad threatened to kill her. Not only was it not true. Step dad had been on deployment the last year. She does things like this all the time and I'm worried about her. The advice I got was make sure someone is with you when talking to her so you have witnesses. Does anyone else have any advice for dealing with this child. And her mom