My mother is impossible!!

My dad passed away almost 20 years ago. At that time, my mother was in excellent health. Now, at 93, she is still living in her own home, but suffers from osteoperosis and the beginnings of glaucoma. Her mind is as sharp as it ever was. My brother and sister live next door to her and my brother has taken on the role of caregiver. I live in another town about 40 miles away. I call her every day (sometimes more than once) and almost always see her at least once a week. So, here is the issue - my brother goes to my mother’s house no less than 10 times a days, prepares all of her meals and takes them to her, and spends the night with her at least 2-3 times a week. My mother calls him in the middle of the night because she can’t sleep so he runs to her like it might be the end. Lately, my mother has begun to have “emergencies” and demands to be taken either to the ER or to the doctor for absolutely nothing. This past week was oneof those times. She is constantly telling me how my brother just “can’t keep doing this without some help” but the problem is my mother want him to do everything for her, but wants me and my sister to be there too. She refuses to use a walker, or get up out of bed and move around, yet she complains of weakness. A few weeks ago I stayed the weekend with her, only to overhear her telling my brother how what I had prepared for her to eat “looked like what you make, but it wasn’t hot.” Everytime I visit with her it’s a lecture about how I have abandoned her because I don’t stay with her at night, when the truth is she wants BOTH of us there. I have said if she is unable to stay by herself for any amount of time we should be thinking about a facility that can meet her needs 24/7. She is right - my brother cannot care for her like this much longer (he is 72) but she refuses to talk about a place for her. He refuses it too. The truth is, she has used guilt to get her way our entire lives and now is no different, except now i dread the idea of soending any time with her or even making a phone call. Every single day our conversations eventually end up with how awful things are and how I never help do anything. How do I respond to the constant guilt trips and her crying wolf without doing irreparable damage?? My sister refuses to give in to any of it, but it eats away at me.