It’s about a girl who isn’t very attractive but has a best friend who is. One day she’s able to start sending her flaws (the first one was a pimple) to her best friend. I think she sends it through a text. Eventually the best friend becomes ugly and has no idea why. I think the magic person who is making this possible blackmails her and says unless she kills someone important to her, they’d tell the best friend the truth. The main character murders her boyfriend and the best friend disappears.

Much later, the best friend reappears to the main character and she’s beautiful again. She said she murdered her parents so she could regain her beauty.

I don't think this is exactly what you're looking for but a one shot called Rokuyoku has a very similar premise!

It's not it, but thank you anyway

Is it the first story of Erotic Horror?

YES, That's it thank you!