I need leading to a good path.

this girl named Lizzie decides to call my friend named Emily a lesbian, because she accidently sat on her leg when she was moving to a seat on the bus, so she could ask a teacher a question. She called her that for the rest of the day. Then Lizzie was being really mean to my boyfriend David, so I told David to calm down and ignore her, but he has this anger inside him that he must let go of. I told Lizzie that if she didn’t want to fight than leave the area, she didn’t, so I told the rest of us to. We moved but than Lizzie and Hannah, decide to follow us!
When we got to school she said, “Ewe, its Isabel” then she said that I have a really mean boyfriend. I felt like cutting her head off and it made me sad that I felt that way and I felt like a sinner. I felt as if I had left god, that I had been selfish and just wanted revenge. I just don’t know what to do, should I do, should I tell on Lizzie tomorrow or let it go. I’m not going to be her friend that’s for sure, because I’ve giving her many chances. But should I just forgive her. What should i do please help me lead gods path.