Your first post sounded, to me, rather patronising, as the daughter of a ninety year old who certainly knows her own mind and would be insulted if I wrote that about her. However, if your mother has incipient dementia and may be a danger to herself if left alone that puts a different slant on it. In that case could you not, as someone upthread suggested, spend the morning with her yourself? You’re not the mother of the bride, so I’m sure the wedding party could absorb your jobs while you do a bit of shopping, have coffee and lunch and a rest before getting ready. I’d be quite grateful for the excuse!