It's more like "someone who's talking behind your back", quite literally, because "Fotzn" is just Bavarian dialect for "mouth" that has really nothing to do with female genitalia. I also don't think it's hugely offensive and a lot of people use the term Fotzn in various ways pretty casually in Bavaria and Austria.
That said, it's still a pretty weird thing to say for a teacher though, that's for sure.
It's more like "someone who's talking behind your back", quite literally, because "Fotzn" is just Bavarian dialect for "mouth" that has really nothing to do with female genitalia. I also don't think it's hugely offensive and a lot of people use the term Fotzn in various ways pretty casually in Bavaria and Austria.
That said, it's still a pretty weird thing to say for a teacher though, that's for sure.