Only your mother can decide what is best for her. Noone else can tell a person what they "should" do? This decision must be based on research by the individual or a person entrusted by that individual. That said, if it were me, I would never have taken chemo in the first place as this is a major barrier for the body to utilize it's own innate healing abilities. If your mother decides to go a natural way, then there is lots she can do.
Start by reading through this forum (click on recommended reading).
Also check out this link which has a very enlightening online free video to watch.