To be honest, it seems like you are having a problem understanding that people come from different cultures. You aren't respecting her culture and her choices and trying to force her to follow yours instead. Its a recipe for disaster and will lead to her resenting you and rebelling in possibly dangerous ways.

In my family, we had no problem straight up showering or changing in front of each other, regardless of gender. When we had family visitors I would have no problem walking across the house in a towel or having full conversations in one. I often wore noting but a bra and booty shorts, and me and my cousins would jokingly tap each other's boobs. We were simply from a culture with much less of the typical American modesty issues.