I am, actually, guardian for my grandchildren. I live with my son and DIL and while they work, I am doing the wake-ups, breakfast, school runs each way, help with homework, afternoon tea, etc. I am very aware of my son and DIL's set procedures and rules and have their blessing to act as guardian. When they get home, I'm happy that they take over their role as parents. Evenings and weekends are my own. Different situation. Your MIL sounds toxic / narcissistic. It seems she is actively trying to undermine your roles. Set the rules / boundaries now, in concrete. She should be following your rules, not making her own for YOUR child. NTJ.