As part of the conflicting beliefs could also be different parenting styles and the child is not willing to adapt. In that case there is no hope unless you want to get downright stubborn - which can be translated as mean by some then it isn't going to work. I doubt mom is working to help the situation as much as she might be letting on because she won't realize what behaviours she is doing or not doing that is actually contributing to the problem.

If you have options then let them go. If you don't and need the income then work with the child at your house in spite of the mom and it may take quite awhile longer. Also realize the older the child gets the more they will mature and understand what is acceptable and not.