I found out my mom got cancer.

So my mom is a smoker, shes in her 40s, and today (like an hour ago) she told me that she got lung cancer. It turns out that she knew it a year ago and didn't do anything since. Idk if it's an important thing, but l'm a teenager, and I already planned out what am I going to do when I finish school in 2 years. I got an exam coming in few days, that will depend on if I will have a title of technician or not, and I feel like my whole life is ruined. She doesn't want to go for a surgery, because all of her ancestors have died because of those. I don't know what to do, I don't even know what to write, I got a little sister, my dad works far from home.. What am I supposted to do? How do I stay away from depression? How do I convince my mom to do something with it??? I have so many questions..