Lesbianism in conservative societies

My friend's sister is a lesbian, but my friend doesn't know, and keep telling me my sister is glued to her friend... She doesn't know it is her girlfriend 🤦‍♀️ Me; awkward smile... I've known for four years now, and the funny thing is that I am not even close AT ALL to her sister, but she just told me one time just like that, and I think one of the reasons she felt comfortable telling me is because she felt I was bi myself. When I first met her, with her then girlfriend, I instantly picked up that this was not a friendship, although it was introduced to me as such at first.. Funny she has had different girlfriends over the years, and my friend still cannot see the pattern lol.