Kimberley Hainey was assessed as being "devoted" to Declan, who was found dead in his cot in March 2010.
His mummified body had lain dead in the litter-filled cot for so long it was covered in dead insects that had been living off his decaying flesh.
The 39-year-old was jailed for life for neglecting and murdering him but released last April on appeal.
Yesterday at a Fatal Accident Inquiry, a senior social worker told Sheriff Ruth Anderson that he and his colleagues, and Ms Hainey, thought she was a good mother.
But referring to a report he had compiled, Hugh Madden said: "She seemed over-concerned for Declan's health and well-being. This is seen as a weakness."
The witness said the report showed that having Declan had changed Ms Hainey's life.
He said: "She cares well and is concerned for Declan and is a good and loving mother."
When asked about heroin addict Ms Hainey's use of drugs and alcohol, Madden said: "She said she only took methadone - no other substances."
But he said in his report, compiled in late 2008, that Ms Hainey had been known to be violent in the past.
The inquiry continues at Paisley Sheriff Court.