I've worked with ovarian cancer patients, as a patient advocate and coach, for several years. The reason they aren't more specific is that every woman is different. Staging statistics are only numbers and represent patients with any level of support, medical access, life conditions, and a thousand other variables that can affect her outcome. Prognosis is very unspecific for this disease.
I've lived with the disease a long, long time. I know women who were diagnosed Stage IIIc over 10 yrs ago and are in perfect health today. Many new treatment options are available that improve the quality of our lives. So my suggestion to you is to look for the best practices of survivors who are living with it and incorporate everything you can into helping her thrive. I've written several ovarian cancer articles for EmpowHer on helpful nutrition, survival tools, managing chemo, etc. These are proven methods that help women with ovarian cancer live longer, better lives. (search my name on this site).
You can get more info on survival of ovarian cancer at www.ovariancancer.org. Mostly, know that you are not alone. We will help you.
Please message me if you want more specific help.