But it would still require a very informed knowledge of researching. Even most college students struggle with such assignments. She most probably had to have had help. But who?
Civil litigators Willie Gary and Mark Simeon spring immediately to mind. As a practical matter you can't file a civil suit against an entire team; you can file a civil suit against a selected few ... and of course, the "deep pockets" strategy is tried and true.
Her attorneys.
No, it wouldn't require a very informed knowledge of research resources. Mangum has some education, so it's certainly not impossible or even unlikely that she wouldn't know about epodunk or some such comprehensive census-specific site.
Specific information on individuals is available in privately operated databases and is available by subscription. Such databases are used extensively by law firms, law enforcement, privates detectives, collection bureaus and a wide variety of businesses.