Me thinks FaranginPetch has been in Thailand too long! Any chance you could get the lady to drop in for a coffee on the appropriate day? Then, as she enters, a gentle sprinkling of water with 'Happy New Year' would be appreciated. Failing that a barbeque in the garden, with a sneak approach from the rear? and Farang's bucket! A cup of water over the shoulder is the civil way to do it, but whatever approach you use, ensure she understands your motives!