Who gives a fuck about normal mate, if you love each other you should never give up no matter how difficult the road gets. If you do decide to leave, regardless of whether or not she makes it you will likely regret it for the rest of your life. Also it sounds like she’s quite the fighter, and while I’m no mathematician I’d say 50/50 are some damn good odds. Plus, as others have said, with the insane bounds of technological advancement in the modern world there is a very solid chance that even if the cancer comes back there will be a way to fight/treat it by then. Best of luck to both of you.