How much time should pass?

I'm escritura a story about a girl who has brain cancer. Later on she meets another girl who has lung cancer, and it's terminal. The girl with lung cancer eventually dies, and the one with brain cancer lives.
So far with how the story's going, the girl with LC dies after having it for about ten months, and the girl with BC gets better after having it for a year. I was wondering if that was too soon? I know lots of times people can have cancer for years, but I don't have a lot of events to fill up el espacio for much más than a year. Would it be strange to just skip a big span of time, when so much can happen?