It could also be due to a misunderstanding or a mistake. For example, she might have been in a place where there was some sort of confusion about who was supposed to be there or not, and as a result, she got locked out accidentally while in an inappropriate state.
One possible reason could be a cruel prank played on her by someone. Maybe there are some mean - spirited people who want to embarrass or harm her.
Maybe she was accidentally locked out while playing in the yard without shoes. She might be waiting for someone to come back and let her in, feeling scared and cold.
One possible reason could be poverty. If the girl comes from a very poor family, she might not have proper footwear. Another reason could be some form of punishment. Maybe she did something wrong according to the rules of a particular institution or group. However, this is really cruel and unfair treatment for a girl.
Maybe it was a dare from her peers. Sometimes, kids do really stupid things because of dares without thinking about the consequences.
First, I would find something to cover her up, like a blanket or a large piece of cloth. Then I would try to find a way to get her back inside or find a safe place for her to stay.
Perhaps she was at a public pool changing area. There was a sudden commotion like a false alarm of some sort. In the chaos, she got locked out of her changing stall while naked. It could be really embarrassing for her and she would have to quickly find a way to get some clothes or cover up.
One possible reason could be that she was kidnapped by a criminal who wanted to keep her hidden for ransom or other malicious intentions. Another reason might be that she was being held captive by someone with a mental disorder who had an abnormal obsession with her.
A kind neighbor might see her and offer help. They could call her parents or try to open the door for her if they have the right tools.
She might be rescued by a kind neighbor who gives her a towel to cover up and then helps her get back into the place. For example, if it was an apartment building, the neighbor could call the landlord to open the door.
It's possible that she had some kind of accident with her shoes. For instance, the heel broke or the strap snapped, and instead of going home to change, she decided to continue shopping barefoot.
She could be barefoot because she was playing a game like hide - and - seek outdoors and got stuck in a bush while trying to hide.