There’s nothing controversial about the answer to this question. It’s straightforward. Hence the comparison to questioning stealing.
It’s not nearly as straightforward as you’re making it sound. I know of some women (and one man) whose rabbanim have permitted them to attend co-ed gyms for various reasons. “Lo Signov” is one of the Aseres HaDibros. “Do not attend a co-ed gym” is not. It’s a terrible comparison.
So to echo the words of flatbusher above, doviddb, ask your rav and not the coffee room.