Why is that an fml? Do you have feelings for her? Saying that she’s your best female friend doesn’t automatically imply that. It’s only an fml if you have feelings for her and she knew that when sending the pic.

Take it for what it is. You said she is your best friend. She trusts you enough to send you a nude for commentary, it’s not often you find someone that’s trusts you that well and on the flip side it’s hard to find someone to trust enough to send that too. I know you are complaining about being friend zoned, however I’ve been there and I am in this exact situation and while we both have our own spouses now, we are each other’s closest friends, supporters and allies outside of our spouses. Don’t squander the trust she has placed in you and you will have a friend for life in her.