9874, my therapist commented once that after my stepmother died I'd get much better and that has happened, as you saw yourself when your mother was away. My stepmother died in 2001 and it's been a really interesting 5 years now. At first I kept grinning and singing "Ding dong the witch is dead!" and making a whole lot of negative comments about my stepmother and would occasionally feel guilty; then, as other, sweeter memories came, I'd feel guilty a lot and as if I'd been too hasty with the first comments and now couldn't take them/that attitude back.
It is you, not your mother who holds the key to how you feel. Only you can be in charge of how you respond to your mother. I found this article interesting/helpful:
http://www.threeminutetherapy.com/chapter.html My stepmother was senile the last 8-10 years, starting with my father dying in 1992. I had some interesting exchanges on the phone where she'd get angry and hang up after yelling at me and then call back in 5 minutes with no memory of the call and we'd start the discussion all over and I'd know what NOT to say that time :-) Maybe you can do that for yourself, after you have a bad reaction to your mother or she to you, write a different ending, a new conversation that cleans it up better and helps you learn how to respond to her more surely, like yourself, instead of like she wants.