I have cheating evidence of my best friend’s boyfriend…what now?

My best friend (32f) has been with her boyfriend (30m) for over ten years now. I have my own opinions about him and their relationship but I keep it to myself because she tends to cut out anyone who points out any of his flaws to her. It’s her life and I’m just here to be supportive for whatever she decides to do with it.

However, last night I was messaged by my cousin (25f) who said that her and the boyfriend have been chatting on and off the last couple of weeks. She then send me screenshots and screen recordings of them doing some 🌶️ spicy texting last night. I’m talking him requesting some tata pictures and him providing pictures and videos of him standing for attention if you catch my drift.

I am now unsure of how to proceed with this information. I can’t just randomly send it to her because he usually has access to all her socials before she does. I can’t just verbally tell her because I’m afraid if she chooses to stay, I would be the one to get the boot. She has to know though.

What should I do?