OJ, I am not an expert in this type of law (although I am a lawyer) but the general rule is that, as the householder, you have the absolute right to say who can and who can't come into your house. MIL has not a leg to stand on as far as I can see. You don't need to get an order to restrain her as she has no right of entry to exercise. That doesn't of course help you with the day to day trauma of dealing with the old cow woman, but would I think be the view that the court would take.
I am so sorry you have this to add on to everything else.