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.
Her pet dog, if she has one, might bark and attract the attention of someone who can help. Also, in some cases, she could call the police or a locksmith herself if she has a phone with her, and they would be the ones to assist her in getting back inside.
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.
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.
There's no way to tell for sure who the barefoot girl is without more of the story. She could be a fictional character created to teach a lesson, like a poor girl from a small village who values the shoes she has and is distraught when she loses them.
She could look for any loose objects in the basement to pick the lock if it's a simple lock. Maybe she could find a hairpin or a small piece of wire.
The house owner could be the villain. Maybe they are a cruel person who likes to exert power over others. They lock the girl in just because they can, without any real reason.
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.
There could be a villain. It might be an evil sorcerer who tied her up as part of a dark spell or to use her for some sinister purpose.
She might be seeking a sense of freedom. College can be a very structured environment, and going barefoot can be a small way to break free from the rules. For example, she may feel restricted by the formality of wearing shoes all the time.
First, we can provide her with proper footwear. Just find a pair of shoes or sandals that fit her and give them to her. This is the most direct way to solve the immediate problem.
There's no way to know for sure without more context. She could be anyone. It could be a fictional character created for a story, or it could be based on a real - life situation where an unnamed girl was in such a predicament.