dissapointment in the form of a friend

i have this friend, that i love alot, she is normally there for me when i need her, but as of lates, she has been pushing me aside.... and i dont know why.... it hurts to think that something said or did can control a friendship as such, but it has.... i helped push her into college, i get a thanks, im trying to help her better herself but to no avail.... i feel as though i am getting walked on, and theres nothing i can do about it