I'm gonna more more jump off a cliff

I feel like I'm getting replaced and its by the worst person. I'm not gonna say actual names so I'm just gonna put their initial. So R used to be my friend but it was from mutual friends and I honestly never liked her anyways later on she started having beef with us, talking about us behind our back, spreading lies, ect ect. because of this information I know dang well she was probably the one that snitched on us. Me and my friend lets call her L had been writing inappropriate things in a notebook and R had asked to see it. L said yes but I quickly took that back for her because of the things R had been saying about us and I didn't want her to use that against her. well long story short she told the counselor about the notebook. another long story short we weren't friends with her but Z had been recently hanging out with her after they connected over a show called Dandadan (another thing is the R cause me and L to be unable to talk to each other and I got moved out of her class and that's why I hated her so much because I was really close to L) Z was aware of this but continued to be friends with her. During lunch today I noticed that Z wasn't beside me anymore and I turned around to see him walking with R I quickly walked ahead not wanting to interact with R. Well Z didn't even try to talk to me and even left me behind (I'm not complaining I just feel like were gonna fall apart because of R) Well time skip we're in the cafeteria I'm barely talking cause I'm uncomfortable with talking to R and Z well knew. I couldn't sit with other friends due to other problems. and I just I don't know. Z is a kinda good friend and we share a few of the same interests. I just don't know what to do