Its very possible the father of the child lives in SM, and she is obligated to live in a certain area. Lawyers cost money even if one person is not paying child support. W/o a good lawyer, people can lose things, like kids. Also, if she had a technical career, her best way to find income again is to stay in the area -- shorter commute, more opportunities, higher income.

Speaking as a once single mom with an extensive technical resume, finding a job can be next to impossible. Regardless, living in the city increases the chance.