In your letter, you sound concerned about the chest pains your mother had. I am sure you are thinking she is having a heart attack! However, if she is having
short bursts of pain, it is more likely to be related to angina, which is a chronic condition. Angina is chest pain that will go away, and usually helped by nitroglycerin. This is different than a heart attack, which is terrible chest pain that does not go away on its own.
I know that you may be concerned about how your family can take care of your mother, especially if she will not go to the hospital. You may absolutely call her doctor to see if there are any other medications that may help her occasional discomfort, or if you have questions. Just because someone doesn't go to the hospital doesn't mean we stop trying to help them! It is just our goals of care are different!
Are you worried about her being in pain? Or dying? If these are your concerns, maybe her doctor could refer her to hospice. Hospice can provide medical care and medications in her own home. This sounds like something that she would agree with, especially since their goal is comfort and not to hospitalize.
You may consult a Doctor at any time, but you must realize that your mother's treatment is limited due to the fact that she has a desire to stay at home.