"I never struggled with trying to figure out what it was I wanted to do or what made the sparks go for me." -Scarlett Johansson
"The girl who mattered." He recited, a breathy laugh escaping past his lips as he shook his head. "Once upon a time… you mattered to me first. Don’t you remember, dearest? When our… dear old Sherlock wanted nothing to do with you?” The Irishmen purred, hands in his pockets as he casually walked toward her. “I could have saved you from the tedium of this life, y’know. But then… you had to become a pretty little liar, didn’t you…” His dark brown eyes sharpened as they locked on her, “Helping Sherlock. Daddy isn’t happy.” He paused. The barest hint of a smile touched the corner of his lips, “Daddy’s. Had. Enough. Now.”
I don’t think Sherlock forgave Mary. I don’t think he simply forgot about it, just because she’s John’s wife. I think he was just acting nice, perhaps for John’s sake.
Yes, it’s true that he hugged her at the airport when saying goodbye, but then again he did think he was going to die. He thought that was the last time he’d ever see John, which was probably why he wanted to make it as undramatic as possible. I think he considered everything. Mary was not done with her assassin job, at least not completely, and I think Sherlock must’ve done something to ensure John’s safety. Perhaps he talked to Mycroft, asked him to keep an eye on his best friend, considering he would never see him again.
Sherlock’s not stupid or naïve, and I think he lost all the trust he had for Mary the moment she shot him. I know he was a bit slow with her- not figuring out who she really was or what her past was like (the only negative thing that could potentially give her away was that she was a liar), but I think it has to do with the fact that she was the first (and possibly the only) John’s girlfriend he genuinely liked. She was snarky, observant and most important of all she didn’t hate him. And yet, I am fairly sure he lost all the respect he had for her in the moment she shot him.
Call me crazy, but I think it’s far from buried. I think Sherlock hasn’t forgot about it- I’m quite sure he even consulted Mycroft about it. It’s even possible they made a plan for what to do in case she’d hurt/kill anyone again. I think it’s even possible they got John in on it, too.