Acne Neonatorum: This condition is common in infants, typically presenting with comedones, papules, and pustules on the face due to hormonal influences from the mother. The presence of discreet pustules on the face of a 6-month-old female makes this a highly plausible diagnosis.

Eczema (Atopic Dermatitis): Although eczema typically presents with more diffuse erythema and scaling, it can sometimes manifest with pustular lesions, especially if infected. The facial involvement in an infant could suggest this diagnosis.
Impetigo: A contagious skin infection that can cause pustules, especially on the face. It's common in children and can be a consideration with discreet pustular lesions.
Milia: While not typically pustular, milia can sometimes be mistaken for pustules. They are very common in infants and appear as small, white bumps on the face.

Congenital Syphilis: Although less common, congenital syphilis can present with a variety of skin manifestations, including bullous or pustular lesions. Given the potential severity and long-term consequences, it's crucial not to miss this diagnosis.
Staphylococcal Scalded Skin Syndrome (SSSS): This condition, caused by staphylococcal toxins, can present with widespread skin lesions, including pustules, and is more severe in infants. Early recognition is critical due to the risk of severe illness.

Langerhans Cell Histiocytosis: A rare disorder that can present with skin lesions, including pustules, among other systemic symptoms. It's an important consideration in cases where the diagnosis is unclear or the patient has additional symptoms.
Incontinentia Pigmenti: A genetic disorder that can cause skin lesions, including pustules, especially in the neonatal period. It's rare and often associated with other systemic findings.