I don't remember reading anything about breast cancer in elderly people, so I don't think it mens to them any more than it means to the rest. Breast cancer is deadly and should be approached accordingly. You dind't say what stage your nana is....There are several stages in the evolution of breast cancer. Here are the stages and the survival rate: 100% for stage 0, 98% for stage i, 76-88 % for stage ii, 49-56 % for stage iii and 16% for stage iv. The only thing you take into account is that your nana is very old, so that means her body is too weak, so the survival rate should be a little lower than above. This is the only difference: elderly people resist less to this disease as their bodies are weak and their immune system is weak as well.
What you should do is take her to a doctor and talk to both her and the doctor to find the best solution. As she is 82, some doctors may not take into account an operation- usually, an operation fixes things- but in her case, she may be too weak for anaesthesia; also the doctor must take into account other diseases she may have that may not allow her to have an operation. Also, her recovery time is double if not triple from a normal one.
You must also consider your nana's wish, as she may choose not to undergo such a thing at her age. This is why you need to talk.
I have heard of natural treatments, but unfortunately I cannot tell you if they are for real. I don't know if they work. But you can try them if your nana wants. However, bear in mind that as time passes by, the possibilities become lesser. So take action immediately.
Also, if you are a female, please know that breast cancer is a genetic disease. And since your aunt had it and your nana has it, every other woman in the family may develop it. So please, do a test to establish if you have the gene that causes this terrible disease and go to periodical medical examination.
Good luck!