Before talking about "stroke therapy" and "vision therapy" for your grandma,you need to know that vision loss from a stroke is not vision loss in one eye as you have
indicated; rather if your grandma's vision loss is from the stroke, which is likely is, then she has lost the right half of her field of vision in both eyes. It is not her right eye that doesn't see; it is that neither eye sees the right half of the world. She sees only the left half of her dinner plate, the left half of the room, etc. This is called a right hemianopsia. The therapy she needs for this is vision rehabilitation with an occupational therapist (not "vision therapy" or "eye therapy" which is usually done by optometrists for completely different problems). Some hospital and outpatient rehabilitation departments have occupational therapists who are skilled at working with individuals with hemianopsias. You should ask your grandma's neurologist or ophthalmologist for help in locating an occupational therapist to work with her.
The fact that your grandma's memory is affected should not mean that she could not benefit from some strategies and it would be very useful for the family to understand and recognize exactly what her visual deficit is and how you all can help her compensate.