Hi Kelen,
As has been said here before, a quote from Mark Twain is appropriate:
"Denial is not just a river in Egypt."
Your family is trying not to understand that Grandma has real medical trouble if she cannot make sense, cannot dress herself, undress herself, and has not recognized her home. She's like a tall 3 year old in trustworthiness. Somewhere inside are a few abilities that may crop up - like driving but those abilities may disappear instantly and she could forget the way home or a traffic law. It's nothing short of a miracle that she got home safely without injury to herself or someone else. Had there been an accident, your family could be held liable for letting her drive.
If no one has DPOA yet, it's going to be difficult unless your state allows a notary public to do this legal document. I live in Virginia and a lawyer who is convinced that the ditsy elder understands what she's signing must do the legal DPOA forms.
Please look at the top of this thread and read the 7 Stages of Alzheimer's, print them, and show them to your family and your grandmother's doctor. There are medicines that can help slow the progress of Alzheimer's.
Above all, you family must understand that Grandma may do anything: metal in the microwave, leave a stove burner on with or without a pan on it, she may take too much medicine or too little, and she may eat constantly or not at all. She needs care and never to be alone - especially in a car with the keys in it!!!!!!!!! Hide the keys lest she leave in the night and drive away. I kid you not! My mother tried that.
Good luck in getting someone to listen. Your grandmother is blessed that you care so much.
Wishing you well - Barbara