My guess is that she was mixing pain pills with the firewater.
I first read an account of the incident, then I heard the audio, and finally watched the video. When I first read about it, I had a similar thought to yours...no shortage of mind altering chemicals being passed around at the Grammys. Then when I heard it, her speech pattern sounded crisp, and her speech was not slurred, merely a mixture of nonsensical words. Finally when I saw the video, it was apparent by the look on her face that she was aware of the disconnect between what she was trying to say and what was coming out of her mouth. I've been around enough drunk, stoned and tripping people and this seemed (to me anyways) something apart from any of those.