Koshea Thats really Sad Mate.
Unmeg has some great advice.
The Best thing for you to do is Listen to her problems and how she's feeling about her father And his illness.It sounds to me like your there for her..
and if the treatment hasnt worked then honestly he's better off cancer is a horrible Painfull Desease..
I know Im on the complete other side of the planet But if theres anything i can do for you mate Just let me know..