Aditya,
We all live on hope. But there are times when it is clear that one needs to move on. Yours is a case in point. The more you roll in self pity, the more you will be disheartened.
You have constantly said that your Love was one-sided and this girl was not even aware of your feelings. It surprises me that in this age, people propose to a girl, without even knowing her well enough to do so. What did you do? Say “Will you marry me” and her reply may have been , but who are you. Before proposing it is essential that you communicate. Get to know a person well and then blurt out your love.
She has made it clear to you that she could be your friend and nothing more. So there is no point in pursuing her.
The fact that she is a year older also means that she is a year wiser and unless it is love, age is always a factor with a woman. She would consider your financial standing in Society and whether you are able to live and earn for yourself.
I am sorry to sound harsh, but I suggest you move on. Concentrate on your career and wish her well. If you truly love her, let her go.