My Mom doesn't smoke but doesn't remember that she doesn't and is pestering us for cigarrettes. Any advice?

My mom is in a nursing home and has been there for about a year. Prior to arriving there she was in another assisted living facility and then in the hospital. During that time, even though she had been a smoker for many years, she could not smoke. They had given her a nicotine patch.

Now she is in the nursing home smoke-free. She has memory issues and thinks she is in her old apartment at times. She thinks she still smokes and constantly pesters us for cigarettes, to go buy her some, to bring her some, etc. She especially pressures my sister who used to get her cigarettes when she lived in her apartment. We always tell her that she does not smoke anymore and she gets angry, refuses to speak to us, threatens to "disown" us, etc. This evening it escalated a bit, because she began to cry saying we didn't love her, etc. We repeat the same things, but it doesn't help. I believe my sister may weaken and just buy her the cigarettes. She had COPD, so that wouldn't be a very good idea, but it's hard to get nagged at continually. If she has cigarettes there I'm afraid she would bug the staff to death to be taken to the smoking area. She was a heavy smoker.

Anyone have any advice about what we could do or say?

Thank you and God bless.