You believe that if you want something badly enough that you can have it; but we aren't dealing with a something, we are dealing with a someone, who has a mind of her own. Your self is actually being destroyed by the mistaken illusion that you are all powerful. The belief that we are all powerful or omnipotent begins in young childhood, a time when we think that we possess magical powers.
All young kids think that if they are good or try harder that they will succeed in changing their crazy parents. When they don't succeed, they just try harder (because their sense of omnipotence makes them believe that everything is within their power). Your problem is that you have never outgrown this childhood illusion. Clinging to it is destroying your soul and could do you in.
What you need is to bring your psyche up to speed or up to date and tell yourself that no one has the power to control another person. If this girl doesn't come around, you are going to need to have the strength to let go and grieve her loss. Oddly enough, letting go is often what it takes to bring someone closer to you! I think you also need to understand more about the life and death quality of this attachment.
I know you love her, but I wonder why you feel that you will die without her. This type of life and death reaction also sounds very young. You know that young kids think that they will literally die from heartbreak. In reality, loss is a part of life. It hurts but it doesn't kill you. You need to understand more about who this girl represents to you (mom, dad?) and how your yearning for her and feeling that you can't live without her relates to your history and the wounds you suffered. Perhaps one or both of your parents was distant or absent when you were little and perhaps you felt that the pain was going to kill you.
When you figure out how your attachment to this girl reminds you of previous attachments, you are going to need to talk to yourself and get some perspective. You can and will live without her if she doesn't take you up on your offer. You will be sad, but you won't die. You need to work on feeling all right in your own skin, even if you are alone. If you can't get to this place of confidence and self-reliance on your own, then do ask a therapist to help work with you on getting there.