Hi,
I am sorry to hear about your grandmothers bladder cancer, but it sound to me that the diagnosis is positive and the best it could be. Superficial bladder cancer is very treatable.
There is a alternative to give her intravesical treatment with Mitomycin C, instead of BCG. Mitomycin is a chemotherapy drug, and there are a few similar drugs also used. The procedure is about the same as with BCG, but the side effects are said to be less. Normally, a 6-8 week treatment once a week is given. Sometimes also maintenance treatment is given. The should be no systematic side effects, as the drug only affects the bladder.
I live overseas and here is Mitomycin actually first choice of treatment for low grade superficial bladder cancer. I have hade 14 doses of Mitomycin the last year. I have not had any BGC so I can´t really compare the two treatments, but my guess is that the local side effect are about the same, but the chance of having serious side effect are much higher with BCG.
BCG are said to be a bit more effective, especially in long term, than Mitomycin.
I am not a doctor, but I think you should ask your grandmothers doctor about Mitomycin. Considering your grandmothers age, it might be a better alternative than BCG for her.