you sound pretty stressed up. Poor mummy. you can try limiting her access to your house by changing house locks n she can only visit when you r home. Instruct your maid to not let her in when you r not around. dont open door n pretend nobody is at home. And disable the doorbell.
your mom can still help to look out for your kids while your maid do the taking care? She's unwell, maybe she can rest, watch tv etc while maid do the work. If your mom is at home, it might be easier to keep a check on the mother in law. But then the best is communication. Tell mother in law what you want n come to a compromise, that is if she's the type who can understand reasoning n willing to compromise.