Sophie and her companion Sid are in Leisure Park when three convicts in a humvee set their sights on them. They attempt to flee, but the convicts catch up to them and bludgeon Sid to death with a baseball bat. Left alone, Sophie runs around the park in a frightened state until Frank helps her.
After being rescued, she will wait in the room with the blue door. When Ronald Shiner complains about the lack of food, he rallies up the other survivors in the same room, including Sophie, to head out and look for food.
If Frank does not stop Ronald's mutiny, Sophie will leave the Security Room along with the other survivors in the same room. They will no longer count towards the number of rescued survivors.
The convicts refer to Sophie as Sid's "old lady", which is slang for a female significant other such as a girlfriend or wife. This is likely an assumption on the part of the convicts. The exact relationship between Sophie and Sid is never specified, although Sophie mentions that she never got to tell Sid how she felt after she is brought to the Security Room, indicating some sort of intimate relationship.
In Chop Till You Drop, Frank helps escort Sophie while battling the convicts through an interactive cutscene with quick time events.
If Sophie dies during these quick time events, the player will get a game over even if Frank is fine.