Will these list of things cause cancer? ( I'm being specific )?

Alrightt...so I have a twin sister and I'm pretty scared for her. She's only 16 years old. She about 4'11. She weighs like 75 pounds. So, she's pretty much anorexic because that's wayyy below the normal weight for a teenage girl. Not only that, but she's pretty much anemic. During her 3 visits to a medical physician for over 3 years, the doctor would always state that her Vitamin D levels are extremely low. So she's pretty much iron deficient. Anyways, she's spends most of her day sleeping. She skips meals a lot. She stopped taking her Vitamin D pills & she pretty much stopped eating vegetables & fruits. Not only that, but she feels really depressed, stressed, and fatigued a whole lot during the day. I really feel bad for her. My worst fear is...Will my Sister contract Cancer/Leukemia or sometype of disease sooner or later? If so what can I do to make things better for her? I really want to help her so Best of Thanks to anybody that answers :)