回复：My boss is not single. He is married.

I am confused again. Have you met your boss at night? Or is it something going to happen?
What your coworker said is her speculation. The fact is to get work done. If I were you, I wouldn't get distracted by her words. It more sounds like that she was jealous of you being in such important position that the boss had to take time away from his vacation. And，"night" might mean sometime between 5 pm to 9 pm. I am not sure if it was her tone or the content of the over heard conversation upset you. If you were not directly involved in the conversation. I wouldn't suggest any speculation further.