Sylvia, if you are living in your own home, then talk to your husband,ask him to back you up with his sisters,and he must say to them,"this is our home,we are looking after Mum, but I am afraid we cannot ask you in if you do not let us know first.We do not want surprise visits."
If they are offended, that is their hard lines.You are the ones doing the caring, you DO need to know.
Please be honest with them, if only to help yourself. (after all, your friends understand. )
Good luck, easier said than done, I know.