How to handle the guilt?

My grandma is suffering from Alzheimer's for past years. Recently, she was shouting more and wanted to leave house, but her legs are not good and the doctor doesn't let her move a lot. We took her outside and she wanted to sit in the middle of the road. We asked the doctor and the doctor prescribed some pills to calm her. After the pills, she was calm and was not shouting, but her situation developed worse. Now she is in her last days, doesn't drink water, can't move and doesn't know what happens around her. I think maybe because of the pills her situation sped up. I even saw in my dream that pills make Alzheimer's worse and I was crying that we killed her. What should I do? We just tried to ease her pain. Now she is dying and everybody at home feel terrible.