my best friend and I got into an argument a couple months ago. After two or three months of not talking at all, despite being in the same friend circles and being in nearly all of the same classes, she has skillfully managed to ignore me at every turn. For a long time I thought that she was acting like a child and that if she was this sensitive, I needed to move on, so I did. Kind of. After some late nights of soul searching, I realized what a massive fucking mistake I had made and how it was all my fault. I texted her immediately and came to the devastating conclusion that she had blocked my number. So in my sleepless desperation I sent her a long, tearful apology on Snapchat messaging. No reply. Three long days went by and I was losing my mind. We are out of school so there is no chance to reconnect with her there.

With my last shred of dignity completely drained, I began to text mutual friends of ours, some of which I barely talked to and only used for sending pictures of textbook pages back and forth. I am THAT desperate. Pitiful, I know. Anyway, it gets worse. It's now been a week since my epiphany and my anxiety is mounting. I can't sleep. I needher back SO BAD. I texted my other best friend, one I've had a close relationship with and for much longer. She promised that she'd talk to the aforementioned best friend, and she did, apologizing since our best friend said she wasn't angry, but didn't think talking to me was a good idea. I'm hopeless. I don't know what to do. I'm so fucking depressed and anxious. Please, please help me get my best friend back.

For context, what did you do? If you want to keep that private it's cool, but in all honesty, if you think it's your fault and you sent the apology then all you can do at this point is wait. If she answers back then that's great, if she doesnt, then that sucks.
As long as you tried your best to apologize then that's all you can do.

Situations like these are tricky, especially when there's not much you can do but hope the other person comes to want the same thing you want. There's not much advice I can give except, wait and give her time. Make sure she understands you're not only sorry for what you did but explain why you reacted that way, not saying this is what you said but for example "I'm sorry for saying and reacting the way I did, at the time this is how I felt and I believed the way you treated me afterwards was unwarranted and petty. I have now come to realise my mistake and how much I value your friendship, please consider talking to me again to help me understand what I can do to help you"; is better than "I'M SO SORRRYYYY I DIDN"T MEAN IT!!!! etc". In the meantime, try and calm yourself, although she's important so are you. Don't punish yourself. You are only human, you need to forgive yourself too and move on from your own mistakes.

Sure. According my old texts—ouch—I said some really shitty stuff and it hurts my heart to read some of the things I said to her. I'm glad I have matured since then.
But I digress. Basically what happened was on New Year's Eve, my other best friend, K, told me that she, first best friend, L, was hosting several of our mutual friends at her house for a party without inviting about half of us, K and myself included. I was seriously offended and instead of asking L like a civilized person, I went off on her. I called her a terrible liar, said she was guilty, and called her a child. I'm cringing so hard right now. My reaction was so uncalled for. I can't believe I said those things to her and I'm in tears right now.
Three days later, I texted L, profusely apologizing for my behavior and she said that she forgave me completely and understood that I was going through some shit (I was, still am, not an excuse however) and that she appreciated

that I was impossibly sorry and it would never ever happen again. Here's a direct quote from her, "I’m so glad we can be on good terms again phew" so she did accept my apology if you are still wondering. But now, six months later, it's radio silence and she told me that my words hurt her so bad it killed our friendship. That was 3 weeks ago. I don't know what to do. I feel crazy and alone and mean and just so, so impossibly sorry.

I know that feeling of guilt, it eats you. Did she ever give you a reason for not inviting you? Not saying that's a valid reason for you going off at her but it helps understand how this all started.

Yes it was just a couple friends it turns out, only 3 that she played video games with literally every day. I've played a video game probably three times in my whole life. It made sense. So now, it makes me feel even worse

Wow, sorry to hear that. There honestly isnt much more you can do besides wait. Give her a while. Maybe she needs time to process. When shes ready, shell reach out

It's okay, rather than knowing that and still lashing out it was a misunderstanding and you believed she was excluding you. I know you feel horrible but those feelings aren't going to help her come back or help you, it's really hard but you need to accept and tell yourself that "it was a misunderstanding, I lashed out, it was uncalled for, I apologised". You were both in the wrong in the end as even after accepting your apology she ignored you, you are not the only one who needs to accept and change your behaviour. Although it may not seem like it now, she values you too, thus why she accepted your apology in the first place so maybe what she needs now is time. She needs time to reflect on your importance in her life. It would be helpful if you could contact her directly, a phone call is always the best choice for things like this, they let real emotion be shown and stop misunderstandings of tone.

I know you asked for our advice but, what to you think you should do? And don't say die, that's not an option here.

Thank you @parisqeen. I don't really want to die at all, I love life, but I'm just so depressed and miserable. I can't believe what I've done. I love her dearly and I hope she does too, she used to tell me that every night before bed. I hope that hasnt changed. I miss her. And I can't even call her because she blocked my number. Thanks everyone for responding.

In time it'll get better, she needs time to process. Keep us updated on anything that happens, try to stay positive if you can.

Thank you so much again, for everything you've done especially the emotional support. I'll let you know if anything changes but my expectations are lowering every day that goes by without word.