Glad you decided to post this here. Hope you are feeling well today.
What a situation. I agree with you and the police, your brother needs to separate himself from her completely. You said it exactly, she doesn't want the help, therefore, she's not going to get it, and she's not going to get well at this point or any time soon, only much worse.
Bipolar is so complicated and your brother needs to seriously stop and listen to what you're trying to say and to learn about what he is dealing with. Because she's not trying to help herself, he needs to separate from her immediately. Things can get so out of hand and dangerous. I wish she would take care of herself, I hate to think of anyone living with this illness and using drugs and alcohol. Your brother needs to even simply understand that fact. The mix of all that is so risky for a lot of things.
It's not his responsibility to take care of her or even stay in her life. I live with an amazing bf, and it's not his responsibility to take care of this whole illness, it is mine.
I am glad you are trying to show him about bp and be there. Keep trying, hopefully he will understand and move on. You're in my thoughts.
Bipolar II, Anxiety/Panic Disorder
--currently not on meds for bp--