Shoulder muscles are commonly used muscle groups, and almost any movement needs its assistance.

People without formal training generally don't have developed deltoid muscles. According to what you said, badminton, although the arm lifting action is remarkable, still belongs to the work without resistance, and will not grow developed deltoid muscles, which will only make your deltoid muscles more beautiful.

Shoulder width is natural, and bodybuilders infinitely enlarge the importance of shoulder width. As women, only by avoiding heavy shoulder work and cooperating with scientific aerobic training can they achieve the goal of reducing fat.

Unfortunately, you can't reduce fat locally. It is recommended to run aerobic for 30-45 minutes 3-5 times a week, eat less high-protein food, control carbohydrate intake, and give priority to vegetables and fruits.