My mom has a lot of issues; well, has had them for a good portion of her life. My older brother & sister (I was sort of an accident at 8 years younger) are no longer in contact with her, so I'm in charge. She's 83 now, and has a long litany of health problems. I moved her out from Boston about 4 years ago to be with us here in California. One thing that has helped, that I think Purple Chicken mentioned, is just letting the negative comments breeze past without really letting them register. A read a "psych" type book when I was younger - I think it's called "The Road Less Traveled" about a strategy to use when you are trying to get through a difficult conversation, and it's helped a lot. I know it sounds odd, but you basically pretend that you are not there, and you ask the person a bunch of questions - focus entirely on them. You are not there, so their answers are irrelevant, but it makes them feel acknowledged & appreciated. Not sure if you have kids, Bantymum, but the hardest part for me has been trying to shield my kids (5 & 8) from a difficult situation. I would never leave my kids alone with my mom, let's put it that way.
Anyway, you are in my thoughts. Take comfort in the good memories you have - my siblings have none of those; since I came along a bit later & was raised by my aunt and uncle, I have quite a few. They (the good memories) are probably what has made it possible for me to maintain the relationship that I have.
Laura