I want an advice about the girl who loves me .?

therz a girl she fell in love with me, I started caring for her whn her sister died , but it was never in my mind that she will fell in love with me, whn ever i try to tell tht i dont love her we r just freinds , she starts crying, so much, now since whn i came to know she is also suffering from brain tumer i nvr discus ths love thinge with hern whnever she says i love i reply same, coz i m afraid if i telllher the truth she gonna die , but i m ruining my life like this, its been a year i havnt had any girlfreind coz of her, but i cant take it anymore, she always weeps and cry, but she also loves me more than anything and is ready to do anything for me, but i dont love her !!! i dont have any feelings , i care coz she is just a good freind to me , she says she's gonna suicide the day whn i leave her. I m like stuck or ... i dono , plz advice me wht shld i do ,