Natasha had decided several weeks earlier that whatever happened in Preya, she wasn't going to let anything become permanent, and she wasn't going to become attached. Attachments were dangerous - she'd learned that the hard way a very long time ago, and had forgotten it when she joined the Avengers. Attachments left you vulnerable.
So as she walked to John's apartment yet again, she told herself that she wasn't attached - she was merely passing the time. Using him, as he was using her. Lying to others was easy, but lying to herself was more difficult, and she quickly pushed the thoughts out of her mind for the time being, deciding instead to just go with the moment. The night had been fairly quiet, and she hadn't yet found any sign of Roxy, so as her shift was ending she decided to head to John's to get some sleep. Just because his place was closer than her own. That was the only reason.
Reaching his apartment, she broke in easily, as she had a few times before. She knew that he had magical wards too, but at some point he had apparently adjusted them so she could enter, and Tasha had chosen not to ask about that. The door opened and shut quietly, and she stood for a moment in the hall to get her bearings and listen for him.
After a moment, she heard the faint sign of television coming from his bedroom, and so Nat headed in that direction, moving soundlessly across the floor, until she reached his doorway and stepped in, barely visible in the dim, washed-out colors of the TV.