I didn't know selfishness was typical until ds went in to a specialist home. The home told us that it is a classic symptom, eg in your last post you put "when your own mother doesn't seem to care for anyone else yet expects everyone to care for her." Expecting the world to revolve around them is one I recognise sooo soo much. Nothing or no one else matters.
It is easy to say ignore it, but not always possible IME, they will carry on until you are forced to do something EVERY TIME. My sister was sectioned about 5 or 6 times before we knew what was wrong with her. On one of those tmes she managed to "escape"
I had to cut my sister out for some time. I wasn't proud of it, but it was the only way I could survive without going under. It was literally a survival strategy. It is much better now she is in a home. Unfortunately you cannot force your mum to have treatment, unless you have her sectioned. Treatment would improve the temper tantrums and stuff though ( the personality issus can be helped by treatment IYKWIM)
I'm really sorry you are going through this BUT your children are your priority. It doesn't mean you don't love or care for your Mum, but Huntingdons is beyond the care or relatives when the illness kicks in.
Sorry if i have said anything to upset you. It is a dreadful thing, and the personality changes of the sufferer are the hardest thing to bear