Given the age of your Lo, this is what I would do.... Ensure she's getting 4 full milk feeds plus 3 meals of solid food. I'm not sure what your routine is like but I would assume bf at wu, around noon, around 4 pm, and before bt with meals roughly 1 to 1.5 hrs after those feeds. Since you can't tell how much she's getting when bf, I would try to make sure she's getting full feeds and then try to add expressed milk or formula to meals however you feel is appropriate depending on what she's eating. You can do breast compressions while feeding which should help keep the milk flowing.
Then with the df, I would time how long you normally feed her and then reduce the number of minutes she's on the breast. If you normally feed from both sides, you can try to keep her on one side first and then start to reduce the feed time in 3 day increments. Once you are reducing the length of time of the df, try to provide more calories at meal times whether it be with added milk to the meals or higher cal foods (eg. Avacado, etc). Does this make sense?