How do you get guardianship of a parent with dementia?

Our mom is 84 years old and has dementia. My two siblings and I think we need to take guardianship of her. She is not able to take care of herself physically anymore and she can’t manage her finances. Her bills are late and her landlord is threatening to evict her. When we mention anything to my mom about helping her or having her move in with one of us, she gets extremely angry. Her neighbors have called Atlanta Adult Protective Services on her a few times when they’ve seen her wandering outside. What do we need to do to get guardianship and what if she keeps refusing to let us help her?