Concerned about my friend?

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So so i have this friend and lets call her J. Me and J are both 14, shes older than me by 5 days. We are in our freshman year of high school. Shes always been in that group classified as the weird and goth people, but honestly i don't care about labels. Shes bi and gets bullied by her "friends" from time to time. I know she has self harmed in the past and we both swore we would never do anything to hurt ourselves again( i have self harmed but this isnt the point). Recently she told me that she tried to commit suicide and went to the hospital and never told me why. I got grounded so my mom took away my phone so we haven't been in touch, and when i try to ask her whats wrong in school or when I dm her on twitter she tries to change the subject. I'm honestly sooooo concerned about her and don't wanna lose her. Shes usually soo open about these things, but this time she isn't opening up. What should I so?