srl8, a goal weight of 115-120 for a woman who is 5' 6" tall and over 40 may even be a bit on the low side and, believe it or not, you are already within a healthy weight range for someone your age and height.
I'm not quite sure if you are trying to get your weight on the low side in anticipation of weight gain when you quit smoking?
Maybe it would be helpful for you to revisit what happened when you quit smoking the last time and think about strategies to prevent the same pattern repeating this time?