Just because the number of maids around the place had lowered didn't mean that Moon Jiwoo's chances of coming upon them gossiping would be zero. At least this time around they weren't all that malicious.
For the most part, they just seemed to be idle chat one did when they were bored, and it didn't seem as if they had intention of looking down her or making their distaste for her obvious. In other words, this was totally harmless.
The gossiping between them was something everyone usually did and not something one should easily be taking offense from.
However, Moon Jiwoo did not consider them to be that light. Coupled with her mentality in that moment, it was understandable why she wasn't able to accept them in a light-hearted manner and took them to be what it was more than that. Even the maids words did not mean as much as she was interpreting from them.