Once you have your brother free, here is one strategy that worked, but it took several years and it will only work if your brother and your father (and any friends or lovers you have) fully agree to this as well so that she can't work her way in through them.
First Saturday in January, you telephone her and say, "Hey, Mom, just called to find out how things are going. However, a few rules first. The moment you say anything bad about anyone else in the family -- dad, my brother, anyone -- I'm hanging up without a word, and I will not speak to you again until the first Saturday in February. You could be dying in the hospital, I won't know, because I won't answer any calls from you or about you and I'll erase any messages you leave me without listening to them or reading them, I'll tear up any letters from you or about you, and if you ever try to come over here, I won't answer the door or let you in. I'll still call you the first Saturday of February, but the moment you say anything bad or you complain about this, I hang up without a word again, and you don't have any contact with me until the first Saturday in March. And that's the way it's going to be for the rest of our lives until you prove to me that you can act like an adult again. Now then, how have you been this month, Mom? I'm really interested, so long as you can behave."
You will probably find yourself hanging up after 10 minutes in January. You will find a lot of voice mail messages or texts from her, but stay true to your word and erase them without ever listening to any of them or reading any of them. On February, your phone call willl probably be only 5 minutes as she tries to change your mind by screaming or crying or feigning lucidity. On March, you may get as much as 20 minutes before you have to hang up. On April, she may refuse to talk to you to see if she break you; thank her for her time and wish her well until you call in May.
The moment she speaks ill of your father, hang up. Do not give her a chance to explain. Do not ask her if she had meant it the way it sounded. Do not let her browbeat you or guilt trip you into giving her a second chance. All you say is, "That was something negative: I will call you in one month," and hang up before she has the chance to say anything in response at all.
Once she realizes you actually mean this, she may decide to ask you if she can discuss this with you and re-negotiate this. Your answer must be a firm, "No, and if you ask again, I will hang up, and you will not hear from me again until next month."
However, never forget to call her the first Saturday of every month. If you do not stick to your agreement to call her once a month on a specific recognizable day, this will also fall apart.
If your entire family can stick to this, honestly stick to it, you may find her behaving like a decent human being before the year is up. But the moment one of you gives in even once -- gives her a chance to explain, reads a text she sends, lets her enter your home as a way around it -- you've lost, and it would be a waste of time to try again. That's why you need to ensure your father, your brother, your friends and lovers are all on the same page with you about this.
At that point, consider her dead, mourn, and move on.
I wish I had an easier course to suggest to you. You have my sympathy all the way on this one.