I think this is a question for the doctor. You should not be doing anything that hasn't been run by a medical professional. Only a medical professional can set up an IV.
I assume since you are investigating alternative therapies that your grandmother has a terminal diagnosis, I'm sorry about that.
I'm sure you have already been researching online but you may not have seen this very concise web page from cancer.gov www.cancer.gov/about-cancer/treatment/cam/patient/vitamin-c-pdq#link/_18
I would also urge you to read Being Mortal by Atul Gawande, a book which includes a very thoughtful discussion about medical decisions at the end of life.
I'm sure you have already been researching online but you may not have seen this very concise web page from cancer.gov
www.cancer.gov/about-cancer/treatment/cam/patient/vitamin-c-pdq#link/_18
I would also urge you to read Being Mortal by Atul Gawande, a book which includes a very thoughtful discussion about medical decisions at the end of life.