Big dilemma which affects my happiness my sanity or one life?

so i like this girl who i go to school with and ive gone and seen her lots and ive built somewhat a thing with her and i decided next time i hang with her im going to ask her out and that day is soon coming but now i met a new girl and got to know her and she sorta fell in love with me over txting i havnt met her either and i got to know her and she has such a terrible life she has lung cancer her indian dad beats her at one house and her mom does coke on the table and her friends bully her every day at school really bad and 4 months ago she even tried to commit suicide but failed and ive been trying to make her happy and ive been more playing along with her acting i really like her and we've made dates and stuff to meet and sorta have a relationship i think. But i wanna go out with the girl here i fear if i break things off with the one girl then she may go suicidal again she tell me how she just wants to dissapeer and thinks every one would be happier if she did i do wanna help her see that lifes worth living and pre much just save her life and make her happy but i also realy want a thing with this other girl before its to late and she get s a boyfriend and i just become a good friend i do not know what to do! please help me yahoo peoples give me some good advice and what ever else you feel the need to tell me about this situation.