likely, your client has some excess weight on other parts of her body but that’s the spot that bothers her the most. Overall fat loss will help reduce the circumference in any part of the body. Adding exercises for biceps and triceps can made the underlying muscles structure firmer and thus improve the appearance of the upper arms.
This is a complicated area for women. While exercise can help, the weight loss has to happen through dietary discipline. And the body has a way of determining where it wants to deposit fat without any consideration from the mind.