My grandma has breast and lung cancer. What is her prognosis with regards to survival rate?

It depends. Ask her oncologist for details. In general breast cancer in post menopausal women has a good prognosis with appropriate treatment. Lung cancer however has a worse prognosis.
Usually breast . Cancer can travel to lung, lung cancer very rarely goes to the breast, and having both as primaries is not very common, but that scenario is potentially curable...The others are not. Treatment may prolong life, or make disease diminish. A lot depends on how gram feels and what she wants to put up with and what her goals are.