Please Read! I need your help!?

A girl named Tatum came to school and we became BFF's! *5th grade* But, after a few months she started gossiping about me to some other idiots. I got real frustrated and she wasn't my friend anymore. I gossiped about her, I dissed her a few times, and I threatened her to stop bullying other people. It didn't work out the way I planned. But, it worked a few times. After that she TRIED to be popular. *She never became popular, she's still trying haha* Anyways, after that, my friend- Sabah, was talking to Tatum. Tatum started gossiping to Sabah about ME! So after they gossiped I asked Sabah what she said about me. I couldn't believe it! She said... 1. I brag a lot! She has way more stuff than me and she brags all the time! If she gets 1 eraser she will brag about it. 2. My house smells? Every house has a smell. Besides, she shouldn't be talking her house smells like dog 3.SHE SAID THAT I SMELL! Which I don't. I take showers everyday, and I use something called Suave Lavender Body Wash :) 4. She made up a joke one day 2 me, and the joke was- You're ugly! I got really mad after that and I told her that was a terrible joke. 5. I made up this joke when I went to a bar with my friend, it was at Main Event, so when I went there I texted Tatum saying I'm at a bar and I'm drinking! *I was drinking water lol* The next day she gets all angry and says- "That wasn't funny." I was just thinking- "You don't know a joke unless it's yours!" I never really talked to her after that. Then Tatum got a cast on her leg. She was faking though! She just wanted attention. My friend overheard Tatum saying- "I just want attention but if I get cruches I will get too much attention." She's still gossiping and making fun of other people. I don't really know what to do. I wanna stand up for myself and when she's making fun of someone, I'm just going to tell her to Shut Her F***ing Big Mouth Up! So In 6th grade, I'm going to talk to her and what should I tell her? What should I tell Tatum? A cool diss, or what? Because Tatum tells her mom on me! IDIOT! What should I do in 6th grade?