In her biography she is full of nothing but adoration for her son.
She mentions a story where she fainted at the studio and Shatner shut down production, then drove her home, carrying an unconscious Nichelle to her apartment. The son answered the door and started yelling "What have you done to my mother, you son of a bitch?!?"
Poor old Bill.
On top of all that, I have always thought that Nichelle had a diva like flair for the dramatic, such as the above fainting
(not saying she faked it for certain, but you never know) and keeping the cast waiting when they were sat in transport waiting to go anywhere.
(Jimmy Doohan said that they left her behind a few times until she got the message). Maybe that diva like flair for the dramatic is part of this.
As you say though, it's a hard call, JB, and one can read anything into a photo. So is that a cold hearted monster looking at her in the top one - or a caring son keeping a watchful eye on her?
But I can certainly see where Ant-Mac and CSM are coming from.