I don't know how I'm going to see my friend now on after today..

I was waiting for my other friend(let's call her A) in front of her house bc she wanted to give me something. It was like 11pm so it was really dark. There's this small playground infront of A's apartment and while I was waiting I heard weird muffled sounds and like slapping(?) sounds. So I turned around to check out what that was and I saw a dark thing moving like, up and down kind of. I was scared at this point because of the muffled grunts and stuff and I was thinking that I'm whitnessing a literal murder, so I pulled out my phone and turned the flashlight on to check on what I was seeing.

There were 2 people, a girl laying down and a boy kinda propped up on top of her, and when I turned the flashlight on the boy and I made eye contact.. Thankfully I couldn't recognize him. He was literally nAked and at this point I knew what was going on. The girl that was laying down then GOT UP and asked to the boy what was going on and looked at me. I COULDN'T BELIVE MY GODDAMN EYES because the girl was my FRIEND.

I didn't think about A and I just ran the other direction to my house and here I am writing about it :(

I don't know how I'm going to see that friend.. We go to the same school and have alot of classes together so I have no way of avoiding her:( plz help!!!