I had multiple complex cysts on my thyroid in my mid 20's. This is what my doc's did.
First I was referred to an endocrinologist. Your Mom's regular doctor should be able to recommend someone.
My endocrinologist first had me get an ultrasound guided needle biopsy of the cysts to make sure they were not cancerous (in my case they were not). Then, he monitored the thyroid cysts for 1 year while I took a daily dose of Synthroid which replaced the thyroid hormones my body should have produced, which kind of put my thyroid on "hold" and could have caused the cysts to shrink.
In my case, after 1 year, the cysts had grown (ultra sounds confirmed this) so I had over 75% of my thyroid removed and have been taking Synthroid or a generic version of it for the past 10 years. My thyroid surgery was in 1999.
I continue to see an endocrinologist once a year for blood work. I had to have my thyroid hormone levels monitored closely during each of my pregnancies.
Generally - thyroid related cysts are not terribly dangerous, even if they are cancerous - thyroid cancer USUALLY does not spread. Thyroid surgery is not terribly invasive, but I did need to spend 3 days in the hospital to have my calcium levels monitored (calcium levels affect your heart - and the glands behind your thyroid monitor those levels). They placed a drain in my neck which was not comfortable, and I took just over a week off work for recovery.
Good luck to your Mom, and I'll have her in my thoughts.
Jessica