If you're hoping this girl will feel bad because you commit suicide, she either wont, or only will for a short time. How old are you? You sound not anything past 20. You haven't even lived nearly half your life yet, and you want to give up because one girl doesn't see you the way you see her.
You'll meet other people. If you're saying your life isn't at the best right now, focus on that instead of a girl. Try resolving your primary problems first. Whatever position you're in right now, there are people out there that are in worse. Whatever situation you're in, it's fixable, or able to be made better. May not be instant, but it's possible.
You can't be lazy or not care or expect things to be handed to you either. If you set your mind towards fixing whatever problems you have, and stick to it, you can. But don't make any irrational decision because a girl you like doesn't like you.