My best friend is doing exstacy, what shall i do??

Hi, umm i just need a lil help my best friend in the whole world has been doing exstacy. i've tried to talk to her about it but when i bring it up we ushally get into a fight over how i have never used it so i don't know what it is like. i want to help her because i love her as a sister and i need her i'm scared something harmful is going to happen. and i don't know if i should tell her mom cuz i don't want her to hate me i've tried everything but i just want to know what would you do in this situation?
Thank You

I would tell her mom. Your friend needs professional help.