Our daughter and granddaughter live with us. They moved in with us at the end of 2017. She has always had a sweet disposition except the last 6 months now that she’s required to spend more time with her dad and his family. Her other grandmother has had 6-7 different boyfriends in the last 3 years. Her dad is a heavy pot smoker and plays video games all the time particularly Diablo. Anyway, I’m worried about demonic possession or contamination of this little girl as her disposition has really changed. My husband myself and daughter pray the nightly rosary together and our granddaughter really acts out and is out of control when we say the rosary. She has a lot of rage too. Anyway just concerned. Do you have any thoughts on this?
In answer to your question - demons can possess children. First look for a natural solution, she is probably acting erratic because she has been affected negatively by the divorce and the poor example of the other family.
Start praying these prayers everynight for the rest of your life - http://auxiliumchristianorum.org/
Read the "requirements" before you start and follow the instructions. These are prayers to drive out evil spirits from your house and children written by Catholic Priest.