My mother has Alzheimer's and isn't a US citizen. She is in assisted living that we pay for, but she needs to be in a nursing home now. Where can we find financial assistance?

Since she isn't a US citizen, she may not qualify for Medicaid, but you'll have to jump to hoops to see. You may want to see an elder law attorney to get some help.
Good luck. I know you aren't alone in this - I hear this questions quite often.
Carol