It was really only by chance that Aziraphale caught sight of the young woman drinking perhaps a bit too much too fast, while on his way back to his company for the party. There's really no time to pass any judgement, not that he necessarily would, before she's simply out of his sight. That's what actually stops him.

He looks around, almost wondering if he had imagined that, did he not spot the glass still on the table. "What in the world...?" He mutters to himself.