`Hey Dorian grey,
I don't know what age you are but I am guessing pretty young if your gf is only 14.
This all seems overwhelming for you right now, right??? You are young, you should be happy not constantly worrying about other people, I don't mean to sound harsh here but I think your gf is being a little maipulative with you, you can't control other people and their actions. You should never allow anyone to emotionally blackmail you with suicide. You GF needs help but you cannot rescue her from her situation, her situation sucks but you have to look after you right now and be happy and I think all of this self harm is bringing you back to a dark place that you bravely left behind once before and I think you know you don't want to go back there!
I know because I have been in the same situation with a GF who always cut herself, we were both young and naive and I cared for her more than myself and did everything to help and everyday she threatened me with siucide I was so distraught I lost 4 stone and became severely depressed and that depression is still here with me today. I told her parents eventually and they blamed me for all her problems even though they hit her. they wouldn't allow us to see each other anymore and it broke my heart.
I don't you to get hurt or blame yourself for not being able to help. She can only help herself now and go to therapy or tell an adult about everything but please be kind to yourself, go out with friends, go to a disco, or the cinema and try to distract yourself from all this