I think it is just fine to let a 2 year old walk around naked. I was going shirtless in the summer months until I was around 6. Playing with the kids from the neighborhood, (boys included). Until my mother told me that I was too old to be doing it. Until that moment, I felt no aprehensions about it. Children are very impressionable and learn from others what is good and bad. If you make a big deal about it, she may feel funny or inhibited later in life. This can include being naked in front of a spouse, or getting undressed in front of others say in school in gym class. She may even decide to quit doing it on her own.