Unfortunately when losing weight you can’t control the areas of weight loss but what I do know is that light weight lifting will do the trick, not only does lifting weights burn lots of calories but it will also strengthen your pectoral muscles making your breasts appear perkier. I would recommend searching weight exercises for pectoral muscles and begin with light weights that you are comfortable with. It’s amazing what a little commitment can do trust me, 2 months ago I couldn’t do a chin up and that really disheartened me as I’m a state level sprinter so generally you would expect me to be fit. but I added just a few pushups a week and can now do about 3-5 chin ups in a row. Wish you all the best