But yes, so far I don’t believe Mary is evil because Sherlock doesn’t think so. And I don’t believe the actors do either.
From Amanda Abbington <about Mary>:
“She doesn’t want to lose John and she knows if this secret ever gets out she’ll lose him. “
“And she does say ‘Look if you come anywhere near me, I’ll kill you’ and he sees this slight wobble of the hand and he thinks that she won’t but I do, but I don’t kill him.”
I think of this next line whenever I hear people insist that Mary was trying to kill Sherlock, but failed:
“She doesn’t kill him, she wounds him. And then calls the police and the ambulance and runs off. I imagine she rushes home, she gets rid of all her kit and she rushed to the hospital, and she knows she hasn’t killed him…”
This next statement from Amanda is important because of so many people have decided to read Mary’s facial expression at the hospital as disappointment that Sherlock survived:
“When John says ‘And YOU I have to keep my eye on you because the first word that Sherlock says is Mary’, it’s like ‘Okay, okay…this is good.’ So this, so… I’ve got to…she has to manage the next part of this story. She knows that Sherlock isn’t going to say anything at that moment. He’s going to bide his time.”
From Benedict Cumberbatch <about Mary>:
“She has a care and love for a man that goes well beyond the darkest episodes and chapters of her past and Sherlock can see that.”
“Despite the big lie of her identity, everything she does she tries to do to conceal her identity to save her love for her man, so he can see the sacrifice.”
—-From Sherlock Uncovered
This is how the actors read the script and interpreted these characters.
This is how they chose to portray it, at least so far. Of course there could be a script being written as we speak that can very us into a completely different direction.
But for now I see nothing that suggests that Mary wanted to kill Sherlock, or Sherlock knows Mary is really evil and is just pretending to like her until the big reveal.
But our theories are just theories, folks. All our analyzation of lighting, facial ticks, actor statements and character comments aren’t going to change the fact that we’ll probably know NOTHING until 2016.