I'm going to cut off my best friend on my birthday
Why are you going to cut your friend off?
I've thought about it and I feel like she dislikes me as a person. She made fun of my weight and body shape before
You're certain you don't want to try and talk it out with her before you do something drastic?
Nah. I want to be miserable on my birthday. It's gonna be a big party.
It's your life, so you have every right to choose who you want to be involved in it or not. I don't condone you seeking misery, but that's on you.