Can I put my family member in a nursing facility if I don't have any legal guardianship or POA?

Hello all! Everyone in my household is currently taking care of my 85 year old grandmother who has advanced dementia. My parents were taking care of everything for her for the past 15 years. Long story short, my father is now disabled and my mother is no longer in the picture. My father never got any type of Power of Attorney or guardianship. My grandmother is declining at a steady pace. She doesn't know where she is or who I even am anymore. I need to place her in a nursing facility where she can get the care she needs. But she doesn't have Medicaid in our state. I currently work fulltime and so does my husband. My aunt who also lives with us, is disabled as well. I'm at a complete loss as to what to do. I have no legal papers stating that I can make decisions on her behalf. Can I put her on medicaid on my own? Do I need to have a guardianship to do so? She has no assets, has owned no property, and does not make enough to be put in a memory care facility.