How do I live knowing I let her down?

HUG. You didn’t let her down. In your heart, you know you did everything possible. You made a judgement call and left, with information you had at that time. In your heart, you have all the answers: namely, you know you gave your best. You’re not omniscient. You couldn’t guess what’ll happen. You gave your best. HUG.

You did nothing to mom to accelerate her decline.
People with dementia fall.
And if mom had Vascular dementia a fall is almost a guarantee at some point.
There were caregivers and they could not have prevented a fall.
Even if they were walking next to her she probably would have fallen.
You being there would have not made a difference.

Is mom on Hospice? If she is on Hospice she should not be going through a "harrowing" death. Frankly if she is under ANY medical care she should not be experiencing pain, anxiety or other symptoms. She should be comfortable.
If it is possible you could bring mom home on Hospice and Hospice will provide all the supplies and equipment that you need, they would arrange to have it there before mom gets there. Hospice will NOT provide 24/7 care caregivers or family need to do that. But a Nurse will come at least 1 time a week, more often if needed. A CNA will come at least 2 times a week to give a bath, shower (sponge bath if mom is not able to get up) and order supplies. And you always have Hospice staff 24/7 by phone if there is a problem or question you have. The Goal of Hospice is to manage pain and symptoms and provide comfort and support. Not just for the patient but for the family.

You can't blame yourself. You did the best you could. Aging, falling, deteriorating and ultimately dying are part of the end of life process. I am not saying this to be cold. My own mom died about 7 weeks ago, and I am trying every day to avoid the "should haves". I did the best I could, as all of us on this forum are doing.

Jane, your post and profile don’t provide much information about ages etc. If M was discharged from hospital as ‘medically fit’, it doesn’t seem likely that she is now going through a ‘harrowing death’ caused by the fall/s. Dementia is ‘harrowing’ for the people that are watching, but although it can come on and get worse rapidly, it often does not lead to a quick death.

You did what you could. If you had stayed in her house, she might still have had just the same second fall, and the results could have been much the same. Not every fall is picked up quickly. You can wish that you had done things differently, and wish that M’s condition could be different, but there is no point in punishing yourself by watching this and grieving over it every day. With ‘advanced dementia’, your presence may not be helping either of you at all.

Plan for the next stage in your life, without carrying a huge burden of (unjustified) guilt.

You DID NOT let your mum down in any way. You all are doing the very best you can under very difficult circumstances.
People with dementia fall...a lot. And there isn't much caregivers can do about that.
For the last 4 years of my husbands life I was home with him 24/7, and he would often fall(as he had vascular dementia)with me right near him or just in the other room. I couldn't have prevented it if I wanted to. Falls just happen.
And just because your mum is under what you're calling "EOL" and I call hospice care, doesn't mean that she's going to die anytime soon.
My late husband was under hospice care in our home for the last 22 months of his life.
Only God knows the day and the time that He will call her home, so just enjoy whatever time you may have left with her and make sure that you leave nothing left unsaid.
God bless you.

My Aunt with advanced dementia fell 3 times, all 3 times she was in her home with family caregivers. One fall she was literally walking and holding on to her niece and still managed to trip and fall and bruise her face. Her final fall was when she got out of her bed in the wee hours of the morning for no reason at all (we had the bed barricaded to try to prevent this). She broke her hip and passed in the rehab, probably from a clot. She was almost 101 yrs old.

Please don't feel guilty. Feel grief, but not guilt. Many a senior has a difficult passing even under the best of circumstances. You did your best to help her in the situation at hand, and that's the most any loving child can do. I wish you peace in your heart.

Your mother was going to fall no matter what you did or didn’t do. My dad had so many falls, some when I was literally standing right beside him. Falls are the curse of the elderly and often game changers. Please stop beating yourself up over what you didn’t cause and cannot change. Don’t assume her end will be harrowing, she may already be at far more peace than you know. I wish you the gift of acceptance and peace

You are not GOD. You cannot prevent the things that happen in life.
It is a sort of hubris to ask of yourself that you are prescient and omnipotent.

I am an RN. I can assure you that falls due to an aging brain and poor balance are often the beginning of the end. It certainly was for my own mother in her early 90s. And it is for many seniors. Any doctor will reassure you that I am ABSOLUTELY RIGHT in this.

I am so very sorry that your mother's death journey is harrowing. I hope with all my heart that she has hospice and that they are providing her with relief and comfort.

You give us few details here, but in any case I assure you that other than attempting to provide her care, which you did, you, as a normal human being with the limitation of being human are not responsible, did not cause and could not fix all that happens at the end of life. You can only be there and hope that there is comfort provided with medication.

I hope at the end of your mother's long life you will allow yourself to feel relief in her passing. She will be beyond suffering and fear. You will not need to stand witness to the torment of one you love.

You didn't cause this. You can't fix this. You are not god.
I wish your mother the blessing of peace.
I wish you the happy memories of a life FULLY LIVED for your mother. I wish you peace you OWE yourself and those who love you. THAT is the way to do your mother honor.

If you need to get help with your grieving, please do so.
If you have Hospice they will guide you to seeing professionals who can help you through.

You do the best you can and go about living your life.

You didn't cause the fall, things like this happen with people who have dementia, the signals from their brain do not operate properly.

Guilt is a self-imposed emotion that serves no purpose, it just keeps one stuck.

What exactly does being with her every day accomplish?

Accept that she will die someday, we all do, I agree with Margaret prepare yourself for the inevitable. Life for you will go on, make the best of it...for you.

How do you live? You do whatever you can to remain healthy and happy, out of respect for your Mother.

Plant a tree in her honor....Make some memory albums, gather favorite photos.

Get through the grief process with a counselor.