Final answer:
For a breast-feeding mother with mastitis, the most appropriate management is to begin treatment with a course of antibiotics such as Dicloxacillin, and continue breastfeeding or pumping to maintain milk flow.
Step-by-step explanation:
The 23-year-old G2P2 who presents with a fever and a tender left breast on postpartum day 10 is showing signs of mastitis, which is an infection of the breast tissue. Based on the description, the most appropriate initial step in the management of this patient would be to prescribe a course of antibiotics that are safe for breastfeeding mothers. The correct choice would be D. Dicloxacillin, which is usually the first line of treatment for mastitis. It is crucial to continue breastfeeding or pumping to maintain milk flow while undergoing antibiotic treatment. Cessation of breastfeeding is not recommended as it may exacerbate breast engorgement and can lead to abscess formation.