Hallo. I have experience of a mother and a husband with dementia, so I understand some of what you are saying.
I did live near my mother for a year or so but then moved over 200 miles away. I was only able to visit about 3 times a year as money was tight. I too had floated the idea of having my mother at home but in reality she deteriorated so badly I knew it was an impossible dream.
I was not with her when she died, and yes there are regrets, but unless your mother had been a very selfish person all her life, she would not want you to beat yourself up. As a mother myself I only ever wanted my children to grow up and become independent, and contented, and living a full life.
It is easy for us to tell you not to feel guilty, and to underestimate how badly you need to say things to her. I suggest you sit quietly somewhere , in your own home, or in the garden, or somewhere where you can be peaceful. Have a photograph of her in your hands, and talk to her. Just say all you need to, tell her how you regret not visiting, tell her how much you love her, tell her how wonderful she was to you, and then just say sorry.
Take her with you in your heart, in your actions in the future, the way you treat other people, . live your life as she would have wanted you to, this is her inheritance to you,. Accept this inheritance, and carry her with you.
When my husband deteriorated he too had to go into care. His brothers could no longer visit, they could not cope at all, they could not even ring him, but they still loved him. My stepdaughter struggled too, but she did visit, and thankfully we were both there at his bedside when he died.
It is hard when your loved one ceases to be the person you relied on, the person you went to with your worries, your dreams, your plans. It is hard. We all know that on here.
Please keep reading, keep replying, and we will support you while you grieve, however long that takes.
Jeannette