Is this something that you must discuss with your mother at some point? If so, make an appointment at a mutually-agreed upon place (agency? Lawyer’s office? )give several options as to time and place. Then, meet and do what must be done.
If you and she don’t have to get together for this, make arrangements, and get it done with the people it does involve ( your brother, caretakers, landlord, whoever is in charge ). Then inform your mother it has been ‘taken care of’. And don’t allow yourself to be roped into an argument! If, the next time you are at your mother’s house, and she brings it up, respectfully inform her that there will be no further discussion, and, if she insists on speaking about it, leave! Yes, she can say what she wants to say, in her own home, but no one who does not want to be there has to be there. I’m guessing that, if you stick by there rules, you won’t be having to put them into practice for too long. Good luck, and God Bless!