There's also epodunk, among others. Mangum is or was a college student, so it's not beyond the pale that she would be able to locate the information, especially if she had help. Further, if she had another kind of help, like somebody with access to one or more of the several good subscription databases that provide information on private individuals such as property ownership, property valuations and mortgages, SSN, and other personal information, it would be easy to find out which boys came from a level of wealth and which did not.
Remember, she'd already had plenty of time to see faces and names on the wanted posters. All she had to do was try to remember what faces were familiar as having been at the party, and then run those family names and pick some out.
That's why it would be interesting to see what was on her computer. Was not her computer part of the discovery requested early on? Or am I thinking of just her cell? I seem to recall some discussion of her computer, though. Somebody? Anybody?
Excellent point. She could have bought such access herself for a day or month for a small fee. Not to mention that in a lot of counties, the assessed value of homes is public information.