How do you deal with an annoying coworker?

This woman is about 50, acts like she's 5. Talks in babytalk during her non-psychotic moments and screams like a banshee the rest of the time. She hardly works, disappears from her desk, constantly emails her husband. She has a perpetual cough and it's like she's yelling at the same time, kind of hard to describe, but really annoying. Nobody likes her, but she thinks she's queen of the office. She's like a dark could whenever she enters a room. They won't fire her, so how can I make her life miserable without getting in trouble?