Hard to follow all of your statement. But I can give you a "guide to cancer cases." First off, they are accurately thought of as "failure to TIMELY diagnose cancer" because, obviously, the doctor didn't cause her to have cancer. So we're talking about a delay in diagnosis and treatment. Therefore we have to determine what the delay caused and distinguish that injury separate and apart from what the cancer may have already caused.
First, you need to have the name of the cancer. Then you find out what stage of cancer it was when finally diagnosed. Then you go to a website like this: http://seer.cancer.gov/publications/survival/. Look up the 5-yr survival rate for the type of cancer and the stage. Let's take an example: we'll say it was lung adenocarcinoma (not small cell lung cancer) and it was stage IV when diagnosed. Stage IV has an abysmal survival rate. But Stage I has a decent rate. Your attorney's task is to prove with hard evidence specifically allowed the cancer to progress from Stage I or Stage II (potentially survivable) to Stage III or IV.
Here's the rub: a delay of diagnosis of 1 month or 4 months or sometimes even 10 months is usually not enough of a delay to be able to prove that the cancer actually moved up to another stage. Ergo, you usually must have a delay in diagnosis of the cancer that is at least 12 months. Of course, this all depends on the exact type of cancer.
From what I can deduce from your statement, it appears that the delay was only a few months. An attorney might have a tough time proving that her prognosis would have been better with an earlier diagnosis.
I'm making lots of guesses here as I don't know the whole story. Also, I'm not a Georgia attorney so I can't tell you about your state's specific laws or the statute of limitations. Consult with a local lawyer to get the best advice. Good luck.
I am sorry for you loss... the answer, It depends. Only after a review of the medical records and investigation can you know if the delay may have contributed to her death. Speak with a local lawyer as soon as possible.