It might seem strange but what else were they going to do inside of a diner with nowhere to go? They weren't going to need to fight. She could, but who knew about John and really, she did the safe place thing for people. If she was needed somewhere, she would end up there. For now, she would just play the diner owner role.
And with the order given, she nodded.
"Coming right up."
So heading back to the 'kitchen' which was actually the control room but anyone in the diner would think it was the kitchen to put in the order, coming back with water at least and if he wanted a soda she could get him that as well.