Hi Everyone. I need help with determining if I'm acting correctly or not. It can get very confusing when trying to set boundaries with someone with BPD, as you all know.

So, the boundary I've been trying to set is that I don't want my mother to mention me to my brother. First of all, I realize that this is a boundary I'm trying to put on her behaviour instead of mine. Maybe I've just answered my own question here, haha! Anyways, this is because he has a drug addiction and a mental illness. She tends to hide behind me (ie. "your sister and I feel that x" about him or his behaviour) and this causes him to rage at me, and saves her from his criticism. He's left death threats and even broken into my house because she mentions something I said and he didn't like it. So I flat out said, don't mention me AT ALL. It was very scary at that time, I actually thought he might hurt me. As if robbing my house wasn't enough. I feared for my safety. She would always "forget" and I had to go NC for a while, over that and other things. He is currently taking care of himself, is not on drugs and is taking medication for his mental illness. This doesn't mean I trust him not to go back to that place he was in before. Recently she told me he was asking about a medical condition I'd told her about. At first I was mad she was discussing my personal details with him and didn't respond. Then I decided to tell her this made me feel disrespected, as I've made it VERY CLEAR in the past that I don't want her to discuss me with him AT ALL, EVER! Of course, oops, she "forgot". It's just such a burden for her to have to always remember to censor herself, she says. I told her it was my opinion that she just didn't care to remember. Her response was to ask about my medical condition again. Oh, the poor woman is just trying to find out about her daughter's illness, but crazy daughter just wants to fight and won't tell her! Boo hoo! Mind you, she had totally forgotten I even had this issue until my brother asked her about it. It's very minor anyways.
I feel like I'm getting sucked in to one of her stupid, boring pity parties and I almost didn't even see it coming. I'm just very mad and don't know where to go from here. I was going to invite her to come stay the night at my new house for the first time in years (she lives out of town) but now I just don't want to be around her. I just want her to acknowledge that she doesn't understand why I don't want her to speak about me, therefore she chooses not to honour my request. Instead of pretending she "forgets" all the time. Well, I think she does forget - because it's not important to her, she doesn't agree with it, and it doesn't make sense to her. She also tends to live in the moment - RIGHT NOW brother is not on drugs, therefore everything's hunky dory.
What do I do? Tell her I'll no longer be telling her any personal information since she can't respect my request? I've been working on building trust and a relationship with her since coming off NC about a year ago, and I feel like this is a major step back.