Please do a search under the following :
"Πρόγραμμα ελέγχου και εκρίζωσης της βρουκέλλωσης των αιγών και των προβάτων"
Underground commerce is prevalent in most parts of the country (I'm in Greece presently), so programs such as the one in the above article, can be implemented satisfactorily only on "legitimate" cattle operations.
This may leave a small number of consumers of dairy and meat products (goat and sheep) vulnerable to Brucellosis.
Some of your mom's symptoms are consistent with
Brucellosis which may be difficult to diagnose.
"Brucellosis symptoms may disappear for weeks or months and then return. In some people, brucellosis becomes chronic, with symptoms persisting for years, even after treatment. Long-term signs and symptoms include fatigue, fevers, arthritis and spondylitis — an inflammatory arthritis that affects the spine and adjacent joints."
--- Source: Mayo Clinic---
I hope this helps.
Did your mom get her ANA Titer checked? Thats done in Labrotory when blood is drawn. Thats a start to see If Its AutoImmune related which I feel It might be tge cause If all infection and Lyme disease is outruled. Prayers and goodluck. Hope mom feels better soon.