Steve knows a full day ahead of time, Tony has known for 48 hours, Natasha isn't told at all. The truth of the matter is that in the two years that Bruce has been gone, Natasha has been too, emotionally. She trains new recruits still, but as more mutants are being added to the ranks, it's an increasingly more difficult task. Fortunately, Natasha was made for difficult tasks, literally, more so now. She's worked extensively with Wanda to parry mental attacks or attempts at mind control or mind reading. It's taken her back to the Red Room over and over again until she moves through the memories like water, slower, but flowing without resistance until she can cut through the other side. This is how she's spent the last two years—hardening herself more than she was, and it seems like an impossible task, and yet somehow that's precisely what she's done. Blue eyes no longer hold that sense of hope and wonder when she'd first started to believe that there could be more to her life than violence and the fury of battle, instead they are cold, calculating, and completely unreadable.
It's served her well so far, Fury has her on a mission seducing a mercenary trying to gain intel into a large weapons dealing ring. She's a few months in and it's gotten...cozy. He talks to his version of Natasha—Aly Roman—pushing for things like living together and how he'll take care of her. In her head, she rolls her eyes, but the blonde version of Natasha with striking green eyes just tells him that there's no rush and that she's an independent woman with a good job at an up and coming software company (that Tony has actually started and funded as a front, and also to give Parker something to do with his time). She isn't looking forward to the party Tony is holding over the weekend (on a yacht, no less) because she thinks he may propose (she did not agree to that, Fury), but at least things seem to be tamer now that he and Pepper have officially tied the knot. The day of the wedding, having to change out of her bridesmaids dress and put in contacts in the passenger's seat of a Smart Car (really, Uber?) had been chaotic and nearly caused a 4 car pile up, all so that she could meet Talon for dinner at Applebees.
The bonus here, is that her fauxlationship has given her plenty of anger to work out, and taking it out at her real job has become something that even Steve doesn't like to get in front of. At least 6 missions she's come back in critical condition—laughing, because Russians don't retreat. Steve reminds her that she said she was Russian and she takes a long pull from a bottle of Tony's expensive vodka that he keeps on the jet and smiles. “It's a matter of circumstance,” she tells him.
On the day that Bruce arrives back at HQ, Natasha is sitting in a board room going over strategies on getting into a large compound—where she thinks the weapons are being sourced based on her conversations with Talon. Finally, she thinks, she can be done with this, snap his neck, and call it a day. Oh, the Natasha that didn't kill people because it was 'bad publicity'? She's gone too, right along with the rest of her give a damn. Steve isn't planning on Tony showing up at this particular moment, and it's clear from the expression on her face when it happens. Natasha goes from cold passivity to an inferno of anger in less than a second. Cap has never seen her so angry that she was frozen in place, but he can feel more than see her muscles tensing and coiling. He moves himself a little to the right to try and at least catch her before she springs. “Tony...we weren't expecting you yet...” he says carefully.
It was the wrong thing to say. “We weren't expecting you at all. You knew about this?!” she demands of Steve. He shakes his head. She looks at Tony and he wonders if Pepper ever found a life insurance company that would cover him. She won't even look at Bruce yet, but she's seen him—a slip of a man, like he was a ghost that somehow found corporeal form. She's standing, and she isn't sure when it happened, but she's aware now that Steve has moved to try and stop her, so she doesn't go for him. She tells herself, she's going to be calm about this. Rational. But her jaw is so tight her teeth might crack at any moment. Even with light hair she's unmistakable, particularly without the green contacts she wears as Aly.