If indeed your grandmother is suffering from dementia (also known at times as Alzheimer’s Disease, though it is just one type of dementia) you need to understand the basics of what is happening to her. Its symptoms involve memory, thinking and social abilities that can affect her daily life badly. Dementia is caused by damage to (or loss of) nerve cells and their connections in the brain. It is almost irreversible. It affects people in their 60's and above, mostly. As a caregiver, your understanding of this disease, its symptoms and caregiving to the patient will make a lot of difference in the conditions of both the patient and the caregiver. People who are interacting with her closely also need to be aware of her condition while dealing with her. Medication from a neurologist or a psychiatrist can slow its progression and improve the patient’s quality of life. With all these as the background, I would suggest you consult a psychologist to get guided on your becoming a good caregiver to your grandmother. I am of the opinion that a psychiatrist or a neurologist can, through medication, improve her condition. If any medicine causes side effects to her, you need to tell that to the doctor and explore other options accordingly. Stopping medicines without consulting a doctor is not at all advisable.
Next Steps
Consult a psychologist / psychiatrist.