Serenity, I hear your frustration in wanting to make things better for your grandmother.
Several issues come to mind.
Your grandmother's move to your house can increase her confusion. Any time a person with dementia has to go through a move, it is very confusing for them. As to the amount of time it takes to settle in, well, it is different for each person. I can understand her using her eyesight as an excuse because this way she does not put herself into a situation she might not be able to deal with. It is the person's defense mechanism that has them refusing to do things.