A 29-year-old woman presents to a primary care clinic with a 4-month history of excessive worry about work, finances, and her health. She reports difficulty concentrating and muscle tension but denies panic attacks or avoidance behavior. Her GAD-7 score is 11, indicating moderate anxiety. She has never received psychiatric treatment and expresses a preference for non-medication approaches first. Using a stepped care model, what is the most appropriate initial treatment plan?