Steamrolled

So as we all know the old saying goes, you hurt the ones you love the most. I never really understood this myself, and continually strive to NOT do this. However, I do see it happening all around me and to me almost constantly. I have a family member who supposedly has a bi-polar condition and it seems like I don't really know whether to believe it or not. When she has an episode it's hard for me to fathom that it's the condition that makes her do it, and I can't understand how she can't control it. The things she does not only hurt her family and kids, but she also tends to hurt herself and has attempted suicide on many occasions, even with her children in the house. Now, as a sister, I completely disagree with the way she treats my brother, and seemingly takes advantage of the fact that she can pretty much go crazy for a day, do what she wants and then apologize and blame it on the disease. He keeps taking her back and I understand that he's in love and has had almost a decade with this woman, so of course he wants to try to make it work for their kids sake. To me, I think this is more harmful for their kids than good. I'm to the point with him that I've realized he's a big boy and can decide how much of it he can personally take, so all I can do is just be here for him when he needs me. The other side of me; the mother, is furious. I don't understand how a mother of 3 beautiful kids can be so selfish to say she's unhappy, wants to go out and do what she wants and do crazy things that they are witnessing. There are alot of things I would like to do, but I realize that my children come first, no matter how unhappy I am I do what I have to until I can find a solution. If she's unhappy, then she needs to fix that, and if she's not happy with him, then she needs to leave and not keep taking advantage of the fact that he is trying to do the right thing. I've always said I understand a medical condition, and I still do, but there's no magic pill in the whole world that is going to make someone ok, if they don't also have the desire to get better to work with that pill. I think she lacks this desire and in a weird sort of way, enjoys misery. I found myself in the middle of a situation this weekend, and trying not to lose my cool with her, even after being shoved down to the ground, and I still walked away. I think it upset me even more, knowing that I had no intention of a confrontation with her, and was only trying to help, but she still could not recognize that and decided to get physical. When I didn't respond back it made me realize something about myself I hadn't realized before. I've finally grown up. I have moved past that point when I would have started swinging just a couple of years ago, and I found myself instead thinking about my kids and where they would be if I fought back and got in trouble, or seriously hurt. I was proud of myself, and also a little embarrassed in a way. I'm not used to letting someone look stronger than me, especially in public, but anyone who knows me, also knows that my actions were the stronger ones. In short, I guess all I can do, despite the pain she has caused me, is to be there for my brother and show him that even with "love is blind" actions he does, he will always have family.