My mom has cancer and needs chemo, but doesn't realize it! help what should i saw to her?

One day at a time: First, you should get information about what kind of survival advantage chemo offers her. Then, tell her: 1) that you need her to stick around 2) that if the side effects are bad, you can always stop the treatment. Take it one day at a time. If the chances of chemo saving her life are one in ten, say: "what if you had to take chemotherapy to save your sister's life? Wouldn't you do that?".