Undoubtedly she had some slight dementia, but for the most part she is lucid. However, she often blurts out her thoughts without regard to who might hear or how it might affect others. many times she is only joking or kidding, but often the other person is offended.
She lives in assisted living nearby, and we often bring her to our house for Sunday dinners. This past Sunday night after a dinner with my daughter and her husband and 3 kids (4 generations), she told my son-in-law that he had quite a belly and looked pregnant. Of course, no one wants to hear this. He is a great son-in-law and has helped in Mom's care whenever asked, and he understands that she is often this blunt, but these comments were too personal and offensive, hurt his feelings, and actually made him angry. I 'm not sure that I depend on his help in the future as I have in the past. All of us were embarrassed by her outburst.
I think I need to discuss this with Mom so at least she knows how offensive she was, but because I am not sure it will have any lasting impact, I am not sure that the emotional cost to her and me will be worth the effort. I think she'll do it again when this episode passes because it's her nature to act this way.
I will appreciate any advice on how to make her more aware and a bit more circumspect.
You could certainly try talking to her, but keep your expectations low.
If having her around is upsetting for others, maybe cut back on the Sunday visits. Try supporting each other with pre- and post-visit talks. Strategize on stuff like how to distract her, change the topic and so on. E.g. prepare yourselves for a insulting outburst, then when it happens, the target can just up and leave the room, with someone following them to offer support (let them vent etc). Someone else can stay with Mom to get her attention focused elsewhere. Find ways to get past these horrible moments that you know are coming.