I [20M] got a boner while in the sauna with my GF [19F] – Now she’s angry and says I disrespected her culture?

My GF is from Finland where sauna culture and nudity is way different than here in the States. She is still living with parents who are first generation immigrants and wanted a built-in sauna in their house which is cool. I had personally never tried an authentic Finnish sauna until last night and well yeah… it didn’t go that well.

I’m not used to seeing the opposite sex very hot in non-sexual situations so well I got a boner while we were doing the whole sauna thing. I noticed that she wasn’t happy with it because she started getting passive aggressive but today she’s opened up avout it being really disrespectful towards her culture and that you can’t just get a boner at a spa or a mixed sauna. I’m not really sure how to navigate this because to me it doesn’t seem like that big a deal but she thinks it is.

TL;DR: We were utilizing my GF’s parents’ home sauna for the first time and I got a boner because I’m not used to seeing the opposite sex in a non-sexual setting. My GF got mad and thinks it’s a big deal but I don’t. I’m not sure how to navigate it.

clarification: it was just me and my gf in the sauna