Is it permissible for a young girl to go to her father or male guests while she is naked, semi-naked, or wearing only a diaper?

There is no harm in a baby girl going unclothed in front of men, as she has no 'awrah (private parts that must be covered) at this age. Scholars have permitted men to wash baby girls and those in a similar situation who are not desired. Nevertheless, it is preferable to cover her body to accustom her to modesty and shyness.