It really is too complicated to explain each and every one of those cards on a site like this, but here are some general things.
Take each card with you any time you visit the Dr. or ER.
Medicare does not pay 100 percent of medical bills. Medicaid does pay full amounts. To see if your grandma qualifies for Medicaid go to your local Department of Human Services office, it is a state program not federal so Social Security does not deal with it.
If she is getting Medicare she has some income from Social Security, the levels for Medicaid are very low but they vary from state to state. In Arkansas where I live I am sure it is lower than California, where I used to live, but it is only about 600 dollars for a single person here.
There are other programs available from DHS also though that may help her such as the one I get that pays for my Medicare monthy amount and qualifies me for 5 dollar co pays on my medicines.
You may want to look into obtaining an insurance that will pay what medicare does not, Blue Cross is the largest company that does that sort of thing.They are called Medi-Gap coverage. They generally cost quite a bit, so you will have to decide after getting the info.
When you get a bill, call the dr. or hospital and work with them, don't just let it go. Sometimes they have programs themselves for low income but if the bill gets old they will not help you.
Ask your local pharmacy about helping you with the new Medicare Prescription Drug Program. Most of them, Walgreen's especially will help you get her into the right program. Depending on income and what meds she takes it will vary greatly. The program is from SS but private companies do it so there are many, very many to choose from.
Also, if she does not qualify for any government services and buys a lot of medicine I highly suggest you contact the maker of each drug to see what programs they have for the low income people using their drug. The income levels they set are much higher in general that the government.
Good luck.