Personally, I'd report the confrontation to HR (in writing) but then leave the ball in their court. While the idealist in me would chafe at the apparent double-standard at play I wouldn't make a stink about that because as a "peon" you're not likely to win that fight, and I assume you want to keep your job. Will she get away without punishment because of her status? Maybe. It sucks but that's life in the real world. But it is also possible that HR is operating in CYA mode because of possible fallout from a physician on their staff exhibiting such a lack of judgment commonly associated with impairment, and that they simply want to keep the entire incident, including any disciplinary action, as quiet as possible.