Hindu Boy wants to get married to a muslim girl

I am a Hindu boy of age 23 years working in a software company since 1 year. I love a girl who is muslim by cast of age 23 years and she is also working in software company since 1 year. We both met in college and fell in love. We are in love since past 4 years. Once before 2 years at her home it was disclosed that we are in love and want to get married. She told her parents but as expected they refused to do so and at that time her parents told her not to contact me and blackmailed emotionally. But still we were together and till now we are together. Since that time she is getting marriage proposal because in her cast they do it early basis. At that time her joining was nearby so she made her parents believe that we are not in relationship otherwise they will not send her for job in outside state. Till now she is refusing all the proposals. From my side all people know from my family mother,sister,brother except my father. They are also telling me not to marry her. They also blackmailed me since that time. abut they can do nothing as I am not of that much age and they can not do my marriage forcefully. We are working in same city since 6 months but never crossed our limits. I truly love her and respect her and want to get marry her. But as I told that both families are blackmailing us emotionally that of we will do like this than they have to commit suicide and what society will tell. All the respect they earned from society will fall down. Now the real problem. We want to get married legally without telling our parents. I read one case on this forum but wanted to know in detail each and everything. 1) Special marriage act and its procedure it's pros and cons and all in and out 2) aryasamaj method and it all procedure. Please help as we are in big trouble. One boy elder than me of 1991 born wants to maary her of her cast and her parents have arranged some meeting. Please tell us the solution so that we can get marry. Required help from law of our country as we people only believe in casts though they are pretending that India is secular. Please help us. Comments are invited