Ditto to dementia being a possibility. People can and do lose their ‘filters’.
Though having said that, an aunt of dh (no dementia) who IMO had always had racist inclinations, started saying things very loudly in public, e.g. ‘So many blacks around here now!’
Not to mention other very loud derogatory comments - ’Why does that waitress wear such short skirts with legs like that!’ 😱
It was a relief when we stopped taking her out to lunch - she invariably moaned about the food anyway - too hot, too cold, too tough, too sloppy, they don’t know how to make pastry any more, etc.
I would take something quick and easy and cook at her flat instead.