Problem in Paradise

On Wednesday morning I got to school and opened my locker and there was a note taped into the inside of my locker. Note: Inside. Meaning: Someone opened my locker and taped it in. I rip it off and read it, it says exactly; "L- The best people are crazy; you are not. You've make a horrible decision. Hopefully you figure it out. -Z" The Z had a line through it... I think it's like a signature. My first thought it was a kinda friend of mine who I won't go into details about (We've already had quite our share of drama), and my trusted friend agreed with me (That trusted friend of mine isn't a close friend but she's very supportive and is kinda like a mother figure in my life). So I went to first block and the suspicious friend of mine was all bubbly and happy and said she had to show me a new guy's text and I directly confronted her about the note. After she said it was absolutely not her and after a moments decision I decided to trust her. I knew when she lied and she hadn't lied at that time. I mentioned to (I'm just gonna call her A) A that the first sentence came from a song called "Mad Hatter" by "Melanie" and so I deduced it had to be from someone who listened to that long. I already had my suspicions on someone (Person B) who hated me and mentioned it. A said that B was already in her suspicions as well. B was someone who used to cling to us and we hated it until I broke it to her that we'd like to have some time to ourselves. And after that, she'd been BEGGING us to let her be our friend. And somehow it happened that she constantly is now around A (much to A's dismay). Obviously she didn't like me as much as she liked A. She sees me as her rival to get A's attention... Which pisses me off to no end. She came up to me yesterday during english when A wasn't here and said, "You must be sad A isn't here, you have no one to sit with at lunch." And I gave her the strangest look and looked her in the eyes and said, "B, I have friends. Im not dependent on one person alone. I've got my boyfriend, Soph, Brogan, Collin, Conner, Elizabeth, Ana, Ellie, and like five other people who I don't know the name of that I always sit with..." And she literally said, "Whatever." Then walked away. If that isn't sad I don't know what is. So A promised me to get some subtle info during English. They sat together while I sat with three of my other friends. Near the end of english A told me she got some info for me, and she told me she asked B if she knew the song "Mad Hatter' or "Melanie Matinez" and B denied it. But she later her B singing the lyrics to the song "Mad Hatter". That's when my suspicions rose. A walked with me to my locker to get my History notebook and then we walked to hers and when she opened her locker there was a note. It said, "I'm so so so sorry! Please don't be mad. I apologize! Im sorry for being annoying. Please be my friend. Please. Please. I was just really excited for my competition this weekend so I rambled. Please forgive me. - B" And it said it was from person B. I gave A a confused look and she told me that she told B that B was being annoying by talking so much and B probably wants to make sure A wasn't mad. I laughed at that and said alright. But this confirmed it for me; the letter in my locker wasn't from B for reason's that now slip my mind. I forgot to mention A earlier told me in first block that on the day before when I was absent, B left her agenda and asked to borrow A's to go to the bathroom. A said sure. And A is the only person who knew my locker combination (Which was why I was suspicious in the first place) and she wrote it down in her agenda (I actually wrote it for her a while ago). And A thinks that B might've used that excuse to open my locker and tape the note inside. But my new theory was that B might've physically put the note in my locker but B's good friend who was a 7th grader who hates me probably was the one who asked her to write it. They're probably conspiring together. After all, the letter B and Z(Im saying Z due to the 'signature' at the bottom) wrote had similar handwriting if not exact handwriting. At least, if my memory suits me correct. Since A decided the letter B wrote was not of importance and tore it up then threw it away (I gave her a lecture after that). But the next day A got a letter in HER locker and it said, "Bitch, BACK OFF - Z P.S show you're friend this" and we were both so confused. We knew that by 'friend' they meant me. We tried thinking anything offended we have done and came up empty handed. By now we had many people gathering info for us and nothing useful has happened. Except for two girls on my bus who I was friends with who were in seventh grade. I told them about the letters and they told me that they know this girl who has a signature with a Z with a line through it. Before they said anything though they looked like they were having a silent discussion because they just looked at each other then one said, "No no it can't be her, she wouldn't do that." And that's the background as to how I figured a third party was in this. And this girl went by the name of person C. My theory so far is; Person C and B and conspiring to get back at me for... Something? Actually, they must be mad at me for telling person B to give us some space... But I think its something more than that because that was months ago. They did say I had to figure out what I did. And this could be an entire prank. But I don't think so. Its very doubtful. But I really did feel like I was in pretty little liars (Except not as intense but let me imagine and pretend). So after that I told A I was gonna get some answers and she asked me how. I told her to tear out a sheet from her notebook and give it to me, and a pencil. She did just that. I wrote "We know who did it - pll" I wrote in cursive the letters "PLL" which stood for 'pretty little liars'. I then showed A and she was overjoyed at my choice of signature. I then told A to somehow slip it in B's locker and we'll see what happens. She was happy to help. And I skipped some minor parts but nothing too major I don't think. I think I wrote this to clear my head XD And now I'm waiting for spring break to end so I can get my answers. And there's always the possibility of it being someone else completely.