Mary didn't immediately notice that she was being watched. She was rather distracted, after all. But the movement through the glass did catch her eye, changing her focus from looking at the glass to looking through it. It was then that she noticed the bearded gentleman looking at her. He was very clearly acknowledging her and it would be very impolite to ignore him. She gave him a smile and inclined her head slightly. It also seemed very impolite to conduct a conversation silently through glass, especially when greeting a potential new friend for the first time.

Turning on her heel, she strode to the door of the shop and pulled it open. Having no inclination to look over the wares therein, she walked right over to the stranger and nodded again. "Good evening."