Over many years I have visited her nearly every day checking to see if she was ok and if she ever needed anything. She was always telling me how much she appreciated what I had done for her but after 2 weeks after being in the care home she has said some things like "If you died , I wouldn't come to your funeral" or "I don't care about you anymore" The first few days in the home were good, she met new people and seemed happy. She turned into a completely different person. Doctors have said she is not suffering from dementia.
If you are visiting your Grandmother the same time each visit, see if you can visit at different times during the day. I read here on the forums that when relatives did a surprise visit, they found their love one actually enjoying themselves.