Dr. Jekyl and Princess Hyde

My mother is a drinker. I don't know where to go from there. There are 32 years of not-so-nice history between the two of us and her little habit. That's not what this is about, though. THIS is about her mocking me yesterday. Slurringly mocking me. Slocking me, if you will. I am not impressed...
You see when mommy isn't drinking she is mommy. She is witty, intelligent and well-spoken. When she is drinking, she is roughly the equivilent of Satan's Sister. (I can say this with some authority as Satan's Sister actually does work with me).
Over the years, I've devised plans to interact with her ONLY when I know she is not drunk. Eg. I don't answer my phone after 6pm when I see it is her calling. I only attend her mandatory family functions until around 2pm. Since she starts drinking at breakfast, 2 is a good time to shag out. You get the idea.
Sometimes, though, she sneaks in on you when you are least expecting it. Yesterday, I was driving home from work. The phone rang. It was mom and it was just now 6pm:
Me: Hello?
Mommy Dearest (MD): Where are YOU? (The word "you" was absolutely SOAKED in venom.)
Me: On my way home from work. What's up? (I always try to remain at my most chipper when she is in this state. I'm not sure if I hope it will encourage her to do the same or if because I know it absolutely enrages her for someone to DARE be cheery when she is so seething with drunken anger. I cheerfully suspect it is the latter).
MD: What the hell ish going on at work? (you see, I, in a blind fit of stupidity, helped her get a job at the same place I work).
Me: Whatever do you mean?
MD: Well, mah bossh just called and shaid I don't have to work morrow. Firsht he shays I do and then he shays I do not. I wish shomeone would tell me when the hell I'm shupposhed work...
Me: He did. You don't have to work tomorrow.

TO WHICH SHE SAID: "He did...You don't have to work amorrow," in a MOST infuriatingly mocking tone.
I hung up on her, panicked about hanging up on her, decided it was a job well done, panicked again and then spent the rest of the drive home thinking about it.
I finally decided after hashing the whole thing over and worrying about what she might do today that it is highly unlikely she will even remember we had this conversation. Although, it's 1:30 now and she hasn't rang as of yet....re-panicking a little... She could, after all, ban my little sisters from coming to see me. Oh HELL!