S.B.
Dear S.,
It sounds to me like either athlete's foot or excema. Believe it or not, athletes foot can look pretty dry and scaly even though it's caused by a fungus that lurks in damp areas. Excema is a completely different skin condition marked by dry and red patches that get itchy.
I would soak her foot in a warm pan of epsom salts because it will feel good and help soak off anything on the surface. Then, dry her little foot and toes really well. Put her on your lap in the sunshine or use a cool blow dryer...but make sure her skin gets good and dry.
This may sound crazy, but rub some vick's vaporub on her foot after it's thoroughly dried and had time to air out. Some swear by it for clearing up nail fungus and also for quieting coughs and relieving cracked heels.
It can't hurt.
Best wishes!