One common element is courage. The girl has to be brave enough to take the risk of escaping. Another is opportunity. There has to be a moment when she can make her move, like when the slave owners are preoccupied. Also, determination plays a big role. She has to keep going no matter how difficult the journey is.
Well, in some girl escaped slavery stories, the girl might have had help from sympathetic people. For instance, a kind-hearted person who worked on the plantation might have provided her with a map and some food. She then used her knowledge of the surrounding areas, which she had gained while working outdoors, to make her escape. She had to be very cautious, traveling at night and hiding during the day. After a long and arduous journey, she finally made it to freedom.
Maybe it was another slave who had more knowledge of the surroundings and could guide her. Or it could be a sympathetic outsider, like a person who opposed slavery on moral grounds and provided her with food and shelter during the escape.
I'm not sure specifically who the girl is without more context. It could be a fictional character created for a particular story, perhaps a girl who managed to escape from a difficult situation like a dangerous place or a bad relationship.
In such a story, perhaps the key event could be the girl's initial decision to escape, which is often driven by unbearable living conditions. Another important event might be her finding a safe hiding place during the escape journey, and finally reaching a place of freedom or a group that can protect her.