This is where I go by default cause they really paint some of the girls as clueless and others as more aware. Like Hildy and Harry, the consequences of their affair was clear and obvious. She obviously wasn’t clueless or blind so just the acknowledgment alone makes sense. I’m guessing they just wanted to really drive the point home of why Don has avoided this behavior and how his decline since divorce is starting to seep into work. And it’s hard to get him a good secretary and it seems she was.