Do you smile? Say hi? If you see her walking toward you, do you make eye contract or look down until she's near? Start a conversation? What do you do if she tries to start a conversation or asks a question that's none of her business? Ignore her? Although it can be seen as rude to ignore them if you've had any previous interactions. Comes across too friendly and she might think you're hitting on her. Not friendly enough and it can be seen as offensive.