Good day,

my mother was diagnosed with stage 2 breast cancer last year and have her right breast removed ( 1 month after discovery ), after the operation the doctor suggest her to undergo a chemotherapy but she was hesitant to do so because of its side effects (falling hair / affecting even healthy tissues / etc ). Then a her friend suggest her to go to a man ( known pastor that practice medicine , (im not really sure about it )). and This man suggest my mother to only eat very natural food and restricted her from eating any kind of food that has any kind of non-natural process in it. 

Im just wondering if it really helps her, because she drops too much weight (Im not really sure if its because of the diet or side-effect of operation ),shes not even taking medicine for cough and any pain-reliever tablet (if she has tooth ache) and when we have a celebration in our house and prepare some food ( ice cream/cake/pasta/viand etc ) she look really pitiful because she is not allowed to eat any of it and we feel sad as well and its been a year now since.

Just want to hear if Its really worth it or it will just worsen her illnesses (because maybe shes missing the nutrients that this foods give e.g beef, pork) 
any kind of advice is really appreciated.