What could upper leg and external (female) front genital itching indicate, for a virgin?

See doctor. You could have a yeast infection, a contact dermatitis or a seborrhea.........so see your doctor for a diagnosis then it can be properly treated,
You may. You may have seborrheic dermatitis. Please see a dermatologist to get the correct diagnosis and treatment.
Many causes. The groin and pubic area may be always moist which may become a fertile ground for a yeast to grow causing itching and rash, specially for persons who are obese and/or have diabtes, also one can develop contact dermatitis( allergies) when new underware, new soap is use if there is hypersentivity to these agents ( new underware/soaps etc..), although not in your case, pubic lice may also cause it.
Typcially dry skin. extreme sweating, and fungal infections are the most common I see. But visit your dermatologist to confirm.