Of course when I read it I could feel my own hackles rising in sympathy. I am reading a book by an English author called Melvyn Bragg at the moment and he has a way of seeing the relationships between people very much in terms of 'power struggles' [even between friends and married couples] which is why it occurred to me reading about your relationship with this annoying woman at the store that the command to love one another is not at all a command to encourage us to become doormats (which is the way non-christians tend to think of the main message of Jesus) but exactly the opposite so that our own 'self-image' is not moulded around the prejudices of others but around the knowledge that we are loved by God and that it is our relationship with Him alone which should colour our relationships with others. By responding with anger to this woman you would be reinforcing her power over you, but by kindness and a generous smile she is utterly defeated. (wasnt it James who spoke of red hot coals?)
still bloody hard to do IRL though grrr :/