Lyn has taken to disapproving of any purchase that Mom makes unless it is food or something for Lyn. It has become quite comical, really.
When Mom purchased a water fountain for her patio a month or two back, Lyn told her emphatically "You didn't need it." For several days, Lyn would grumble and mumble and scowl each time she saw it.
Yesterday, Mom picked up a set of wind chimes while she was out running errands. Lyn heard them about 5 minutes after arriving home. She didn't say anything at first but started to stew. After about 20 minutes, she was ready to chastise Mom. "I hear wind chimes." Mom said "Really? I don't see any." Lyn countered with "You always buy something you don't need." She got up and looked out the window where the sound was originating.
She was angry by the time she returned to the rocking chair muttering to herself about how "you always buy things you don't need." Mom reminded Lyn that Lyn's money is not used in the purchase and perhaps Mom did need them. Lyn decided that wasn't good enough and stayed mad for over an hour.
Mom had a hard time not laughing during that hour. When you cannot reason with the dementia, it is better to be amused by it.