It wasn’t so much that Mac was surprised that someone had stopped to speak to her. She was casually friendly with many people from the bus. It was more who was talking to her. After being on the bus for a couple of months, Mac was very aware of who Bucky was, but she also knew he talked to about as many people as she did. So for him to come up to her out of nowhere and stop doing whatever important thing she was sure he was in the middle of to talk to her was more than a little startling.
Covering her confusion with a frown, Mac managed to not sound sarcastic when she spoke, which really was a feat considering it was her typical defence mechanism. “No, I’m not busy.” She may have succeeded in not sounding sarcastic, but she most definitely did sound confused. What in the world could the super-powered second in command need her for?