My mom and I live with my grandmother and she is now convinced that someone is smoking in the house. My mom doesn't smoke, and I don't smoke either. It has gotten to the point that I can't even go downstairs without her asking who's smoking upstairs. She calls me a liar and keeps saying not to tell her that my mom isn't smoking. I don't know what to do. She always looks out her window to see when we are coming and going and then she closes her door whenever she knows that my mom is home. What can I do? I don't know how to handle this anymore.
The most common kind of hallucinations are visual. Some people have auditory hallucinations. It is rare, but it is also possible to have olfactory hallucinations. If your grandmother is smelling something (cigarette smaoke) that isn't really there, no wonder she thinks someone is lying. The smell is very real to her, just as visions are very real to people who see them.
I don't know whether this is part of your GM's already-diagnosed dementia, or if this is a separate issue. Is her doctor aware of this development?
I wonder if there is any way you could acknowledge that she really is smelling smoke, but that you and your mom are not smoking. That the previous owners were very heavy smokers and now that the carpet is wearing down it is releasing the built-up smoke particles. (I'm really reaching here ... I hope you can come up with something more plausible.) You don't want to call her a liar -- she really is smelling smoke -- but you want her to trust the people she is living with. It is tough!
Discuss this with her doctor.