Mac, my youngest daughter was bipolar. And she was the mother of five children. She is no longer with us. Every time the phone rang, I wondered what did she do now. Do I have to go pick up the children again? Did she try to kill herself again? Is she forgetting to take her medications again?
The last phone call I got about her was to please come and pick up her kids and identify her body. She had been murdered. So I can understand your frustration. But I have one consolation. I do not have to live with the "if onlies." If only I had ..... Living with someone who has a mental disorder is a difficult thing to go through. You never know what to expect. What surprise is right around the corner. Your sister cannot help the way she is. And it is not how she wants to be. I can't tell you how many times my daughter would ask me, "Ma why do I do these things? I hate myself after when I do them."
Try to be patient with her. It is not easy. But in doing so, you will never have to live with the "if onlies." If you feel like you are at the end of your rope, turn and walk away.
There is a little trick that members of AA practice when they are with someone who needs a drink really bad but do not want to take one. Someone sober will stand next to them and give them a light backrub with one hand while talking to them all the time. It calms the person down. I don't know why it works, but it does. I have seen it time and time again. I learned that trick when my kids were really small. An AA member told me about it more than 50 years ago. I used to use it on my daughter. I used that trick on my daughter when she was about five years old and right up to when she died. It is amazing what a little affection from a loved one will accomplish. And it works great on a small child that is having a temper tantrum and out of control.