My lovely MIL died about 4 years ago, of cancer. A couple of months before she died, she was in a hospice, in Southampton, and it was obvious that the end was near. I travelled down from Scotland with ds2 to see her, and we met up with ds1 who was at Reading university. We asked ds3, who was about 17, if he wanted to come too, and after thinking it through, he refused.
He didn’t want to have his last memories of his grandmother to be her so ill and unlike herself, and we respected his choice, just as we respected the choice of the other two, to see her and say their goodbyes.
The reason I am telling this story is that, in the years since her passing, none of the boys have said they wished they had made a different decision. I did worry that ds3 would regret not saying that last goodbye, but he hasn’t - nor do his brothers regret seeing their grandmother.
Unfortunately this means there is no one clear answer to your question, @thecatsarecrazy - unless it is to say you should follow your heart. Do what you feel is best for you, even if that is different to your mum’s decision. I am so sorry you are going through this. 