I need help understanding why this girl is the way she is.anyone please explain?

ok so theres this girl right?she was the girl i really loved, never felt this way about any other girl. i couldnt stop thinking about her, and she was on my mind. i finally get the chance to tell her i like her alot, and she doesnt give me a chance.i was always the repecful guy, always checking to see how her day was, any problems, we would talk for everything. she would call me, i would call her, i felt it could have gotten me somewhere. Then this guy comes along, from what she tells me she likes this other guy because he treats her like crap. he does weed, very disrespectful, tells her F*** you instead of i love you, he is real stuck up and well just terrible. i know im not one to judge but thats what she told me and thats what ive seen. for those of you who want to know how i am this is me, im respectful,loyal,lovable,i could get along with people easily, i have my career plans set out, im laid back but i do what i have to do,when i say im gonna do something i do it. so yes no exaggerations that is me. so please, people tell me, why didnt she find intrest in me? yet she fell for the pothead,with nothing planned in life that treats her bad? thanks to whoever can explain this to me :)