How to convince her..?

i saw a girl in fb.. she is in my friend's list for the past 1 year.. bt last 3 month oly we were.. and we became too close... coz of my earlier one sided love... i was totally fec up on ma life and and this fb girl is the one who gave me a new life... she is the one who made me smile again... and my friendship towards her became a love... again a true love... bt the sad part is she is committed... and nw her relationship with her guy is complicated.. and she itself told me tht she gonna break up with him.. as for him, she s jus like a show piece... at this time.. i proposed her... i told as much ever i can... my love for her is true very true... even i m ready to give life for her... definitely i cant live without her.... bt she is not accepting my love... she says... even if her guy is not loyal to her, she break up with him and wont get into any relationship. with anyone...! she tells me, tht "i knw u can keep any girl happy, i like u... bt i cant love u, i dnt have such feeling for u...!!! i spoke spoke spoke a lot.. bt still no use... atlast she started shouting at me... and told me tht, she cant be mine never..!! i feel very bad nw.... i feel like dying... y no one is realizing the true love..... i want to be in love... pls help me... i need her... can some one tell me.. wht can i do..?