My Friend Roped me Into A 2-Week Long "Character Story" Lie That Is Ruining My Friendships With A New Friend Group

I (17) and my friend (female, 15, close to 16) have been friends for a few years now. She has always been a very imaginative person, and has always been trying out new things, sometimes taking inspiration from others. We hang out a bit, usually through games like Minecraft, or Monster Hunter Rise, and recently, she introduced me to an active chat with her friends on Padlet. At first, when I joined, I did think she just wanted me to meet them, see what they were like, maybe stay in the chat and make some new friends.

But then things got strange. A few days after she invited me in, she told me about a "character story" idea she got the idea for after her friend had done something similar. She wanted me to take the role of one of the characters she had made, Noodles, and act like there was someone controlling what we do, that I was "created" by an entity with no name that I was supposed to just call Them or They (like the pronouns, but capitalized). At first, I said sure, because it seemed like this might be fun. It was at first, joking around, making padlets for a "secret" nobody could figure out. I thought it would last maybe a day, a few days at most. But then it kept going, and going, and after a week and a half I felt too deep into it to get back out or apologize, because there was no real clean way to escape this. Finally, a earlier fight from before i was invited in between my friend and one of her friends in the group was brought up again when my friend got on to the chat, and things got intense, with my friend not taking anything seriously, and her friend going into a suicidal spiral, not able to take it anymore.

Now, everything is falling apart, my friend won't talk to me again, thinking she killed her friend by not apologizing, and I'm scared of what will happen if I go back to the chat. I don't want to lose the friends I made, but I'm not sure if they will believe or accept any apology I give since they only knew the real me for a few days before all this started. What should I do, and how do I apologize to everyone for the lies my friend started and for my involvement in all of this?