My best friend cheating??

Aight. Bit of a story here. Thought I would post here cause she doesn't use this app (freaking hope so)

I've been friends with this girl since I was very young. She's in a band with me as well and we can't afford to lose her talent, which is why this situation is very hard.

She asked me to do her streaks on Snapchat for her, and I thought I may as well. So I login, and me being me, I go through and Snoop through some of her messages (I know I shouldn't but I do anyway). She's been dating this guy for 6 months (literally yesterday), and he's one of the kindest people you'll ever meet- and my boyfriend agrees.

Well, I look through these messages and find around 5-6 guys that I believe she has been cheating on her 'man' with. I'm not just talking kiss emojis and love hearts, I'm talking full on sexual videos and photos from both parties (which I wish I hadn't seen).

This one guy decided to send a boxer pic, not realising that she had asked me to do her streaks and freaked out in the chat apologizing. So I thought I would ask this guy a few things. He in fact confirmed that they had been 'dating' for quite a while now, and I believe this because she has written heaps of I love you baby to him and he has written such in return.

So, I didn't want to confront her, but after this I absolutely had to. It's not right.

I messaged her and explained that this guy had messaged me saying that he is her boyfriend and that he wanted me to tell her he loved her and yada yada. Her response was that she 'gets that a lot' and to just ignore it. She told me she would never cheat on her man as he 'deserves the world'.

I left it at that cause I didn't want her to get suspicious that I had read her messages and seen blasphemous things (I now want to wash my eyes out with bleach).

The thing that's even worse is I'm 90% one of these guys is around 24 years old, and she is 16.

So, I'm stuck. She told me not to message her boyfriend but I'm seriously thinking about it. I have proof.

But, the thing is, she will take it out on me (she's having a bit of a tough time right now), and will most likely leave the band and never speak to me again.

I'm stuck in a loop and I just want answers!! 😭 any advice on how I should proceed??

(Yes I know it was none of my business to read through her messages but as an acquaintance/friend to her 'one and only', I would feel too bad just leaving it. Please don't send hate)