I teased her once because she had a hickey on her neck. (All I did was ask her what's that mark on your neck. She looked embarrassed and came up with some lame answer. I looked at her mom and we both snickered. My niece knew then that I knew what it was and she laughed too.)
The only time I said anything was when she mentioned it to me. She said she wasn't going to live that lifestyle forever. She thought the people were weirdos -- especially the men -- and she wanted out. She thought her girlfriend was a nice person and everything, and that there was nothing actually WRONG with it, but she wanted out. I told her that I thought it was wrong but that I loved her anyway because she's my niece. That's it.
She shot herself about two months after that conversation. She was almost 22 when she died. Was I right to stay silent? I don't think so.
I think that you did the right thing. Sounds like you were her friend, what she most needed. I’m sorry.