Turn into a tourist
So what if the two of you know everything about your city. Just go on a long drive through the city. It you live in Mumbai, stop at Haji Ali and watch it from a distance and spend some time near the sea, watching the waves come and go. Go to any joint which the two of you agree upon, have a leisurely meal and buy some stuff from the street-side as you walk hand in hand after dinner. It will be a nice experience that she will love for sure.