I am confused-is there a difference between severe cognitive deficit and dementia?

I am confused. My mom, breast cancer that metastasized to brain, received whole brain radiation almost 5 years ago. She has had a decline in cognition. A month ago she was dropped by an aid and fractured her tibia in three places. She is currently in rehab but has been labeled severe cognitive deficit. They are not calling it dementia but blaming it on the effects of the radiation. I agree that is the cause but is it not still dementia? And what does this mean as far as her care? Will she be eligible for hospice or will I need to consider a long term care facility? We have tried so hard to keep her home.