Her son, Garnett died in 2014 at Westchester Medical Centre after he was treated for gastrointestinal symptoms that Spears had induced.
His feeding tube had been in place since infancy when Spears told doctors he could not keep food down.
The prosecution said that having administered him salt at their home in suburban New York, she twice took Garnett into a bathroom at the hospital to do the same. They said she posted pictures of him dying on her Facebook account.
Acting state supreme court justice Robert Neary called Spears' crime "unfathomable in its cruelty'', bringing Garnett "five years of torment and pain".
Assistant district attorney Doreen Lloyd said: "She continued to portray him as a sick child for her own bizarre need for attention.
The judge described her as mentally ill and identified her condition as Munchausen by proxy syndrome, in which a person, usually a parent, sickens a child to gain attention from the child's plight.
This woman was really sick and cruel beyond any imagination.