Why is my mother in law my best mt8 one week and arms length the next this drives me up the wall shes wierd?

It's not you, it is her and you won't be able to change her. Do yourself a favor, and visit only when necessary (holidays) and stop trying to make her like you. Use good manners, of course, and help when necessary, but stop the rest. Your husband knows that it is hopeless, and you should listen to him. If his dad is nice, just talk to him.