Suicide is definitely not the way to go. Life has a more meaningful purpose and remember you always have this one chance to live life like this. So live it to your very best and always know that something is going to turn out better, if only you make the effort to make it better.
So search for the courage and confidence deep within of you and start with your new life, what's up with the girl anyways? It's only one flower in an Eden garden, there's plenty of flowers everywhere, you just didn't look hard enough! Ignore her, and trust me, if she really does have feelings for you, she'll come back, because she misses the feelings you have given her. If she doesn't, she was never meant to be yours, and it's time you move on anyway.