It sounds like an honest mistake.
Mortgage, title, and other real estate documents are public record. You should be able to look into the property history and current documents on the property appraiser's / tax collector's website in the county where the property is located. If they don't have this service online your mother may need to call. She should also have copies of the loan docs, deed, etc., and should be able to verify names on the docs.
If the names on the docs are correct and the docs are current (no newer refi, etc) then it should not be difficult to provide the clerk with the proof of who owns the property and have the county property appraiser / tax collector fix the clerical error.
In case my terminology is incorrect, down here in Broward County, Florida, the website for the county property appraiser is
http://www.bcpa.net. I imagine most counties these days have a similar website where you can look up property records.