Talking to my mother with Alzheimer's?

Threee years ago my mother was diagnosed with Alzheimers Dementia. Her doctor informed us that her condition would slowly worsen. My mother remembers all of her children, but only as babies. She thinks that her husband (who is deceased) is still living. The other day, I got off work to find my mom depressed and very upset. The rest of my family members wanted me to help them to convince mother that Daddy was dead. My mother was crying and called them liers, because she had seen daddy that morning . I informed my mom that daddy was not dead, and that she did see him, but he had gone to work. That caused her to smile and brought peace. My family says that I was wrong for not telling the truth. They keep my mom depressed, trying to explain things that mother no longer see.My mother and I have long conversations, because I talk her way. She is happy with me around. Was I wrong for not telling my mother the truth?