My mother was moved into assisted living (not a nursing home) two weeks ago. She is 81 and receives her retirement, some of dad's retirement (he passed 5 yrs. ago) and, her social security. Should her house go back to the bank due to nonpayment (she can't afford both places) because of the poor real estate market here in Florida (it might not sell), could her income be garnished ? She has a diagnosis of dementia and it is starting to appear to be more like alzheimers.

It depends who is garnishing it. Social security can not be garnished except by government, student loans and I believe a couple other things possibly. Credit card companies  can not garnish social security. I think the retirement money can be garnished.