I think sometimes family tries to do whats best for family members in need because they feel indebted to them. I also think that its not fair to any family members to feel trapped by a decision that is not made in a family as a whole.
It sounds to me that your Mother needs round the clock professional care --preferably a nursing home or some such facility.
When my Grandmother was dying, my Aunt cared for her day in and day out until she passed. But looking back, maybe we should have had someone come in a few times a week to check on things. I remember walking in the door and the smell of sickness filled the air. I can't say if her personal hygene needs were being met. I think my Aunt was more lienant with her because it was her mother. It was not a professional relationship.
Don't feel guilty about your decision. If something happened when you were caring for her then you'd hear about it from others forever. I'd bow out and suggest alternate care options to your family.
Wishing you peace and strength.