Taking care of a child is completely different than taking care of an adult. Consider lifting (an adult is significantly heavier), bathing, cleaning their diapers, etc. You add to that any medical, physical or mental difficulties.
Just physically there is a huge difference. Also, a parent decides to have a child, a child does not decide to take care of an adult. To be honest, as a parent currently, I would not want this burden on my children. I would not want my children to have to take care of me in such a way. I love them too much. I would like to think they would be there for me as in to visit and spend time with, but I wouldn’t want them to physically take care of me.
Unless you are a nurse and have the skills and knowledge of taking care of an elderly adult, a nursing home in many situations may actually be better for her. My mom recently went through this with her mother (and she is one of eight) " no one else would take her in. Only one other sister helps out. It was too much for her " she is now in a nursing home " getting the care that my mom wasn’t able to give her. She isn’t abandoning her " she is visited by my mom, and her sister regularly along with some of the grand and great-grand kids.