Help for a friend

I have a friend that has been going through a bad time recently, losing her two best friends. She has self harmed in the past and threatened suicide. I'm extremely worried about her. I have suggested this app, threapy, self care, even going outside to take a walk every now and then or taking care of a plant but she refuses help and I'm don't know what to do anymore to help. She's so stubborn and insists that she will talk to one of her friends again. I have been talking with him though and he continues to say that he doesn't think it's a good idea and it won't go the way she wants and I agree with him but she refuses to accept it. Does anyone have any idea of what I could try? I don't want to leave her behind or just stop talking but it's starting to hurt me and I don't know how much more I can take of the strew from trying to help her but she's like a little sister or daughter to me.