I hear what you are saying. I am a polite person and smile and say hi to people. There is nothing wrong with being nice and I do not think she is saying that woman is wrong for being nice. There is a fine line with being pleasant and smiling, saying hi and when someone feels as though you have to sit there and talk with them for 20 minutes to an hour.
Sometimes we might just be in a bad mood, sometimes we just had a busy day and do not feel like socializing and there is nothing wrong with that. If I go to the coffee shop to escape for a few minutes and have a few minutes of alone time, just because I am there and by myself does not mean I have to be forced to engage in unwanted conversation with the person next to me whom I do not even know. I should have good manners and be polite, smile and say hi but people should also understand sometimes strangers do not want to sit and talk with them.
Being polite and having good manners goes two ways. Make polite conversation but do not hold someone up from their day or make it so you are infringing on their personal space and personal time.