I feel my grandmother is being abused. What can I do to prove it?

You don't say exactly why you feel your grandmother is being abused. If she is in a home, the staff usually meet physical needs but not emotional ones and can be short and abrupt. Unless there are bruises or someone witnesses a situation there is not much to do. Be grateful she is not trying to escape and go to the bank like my 91 year old mother who is blind and wheelchair bound. Pray for her and remember - she had your life, and you need to have yours. Also depending on the person they like to have people worry or feel sorry for them and can sense the guillt... so think about how you act when you are there are what she is really telling you.