How can I get mom full time care when she refuses to "spend down Medicaid" and also cannot afford an aide as well as a nursing home?

Who is in control of her finances?
If it is you then do what you need to do.
Spend down what needs to be spent as long as it is for her care there should not be a problem.
Contact your local Senior Center, Senior Services or other local agency to determine what help she/you are able to apply for.
But again..she has dementia, she can not make sound decisions for her safety and care you need to make those decisions for her.

Your forum name and your profile are dramatic and scary. You have a history of being abused by your mother and the only solution you see is for one of you to die?

In what shape is your mother? Does she have health issues? Dementia? Other mental issues? Where does she live? If you can be honest with her, she needs to hear that she needs more help than you can offer. If she can’t be reasoned with, you’ll need help. Do you have sibs? A spouse? If neither, a trip with her to speak frankly with her doctor may be necessary.

If she is like my mom. They are very frugal! They don’t wish to spend a dime more than necessary.

They recycled long before it was fashionable to do. Nothing in their generation was wasted.

My parents lived through the depression and I think they could never forget it causing them to count every penny.