Just also chiming in that as notorious as this case may be to those "in the know", very few people would know it out in their normal, everyday lives. I only found out about this after becoming interested in Does after stumbling across the DNA Doe Project website and spiraling down the rabbit hole until I ended up here.
When I told my parents about WCJD, who are two very knowledgeable people about crime cases since they had the dubious honor of living in California back when all the notorious killers were at work, they had NEVER heard of this case whatsoever, not even from our many relatives who live in Texas. Also of note was my father was of the opinion her response of "Who cares?" when asked about where her parents was that it wasn't just a smartass quip from a teenager, he thought sadly enough (and was probably right) that her parents legitimately didn't give a hoot about where their daughter was or what she was doing. Unless they were young parents, both of them are probably deceased by now, and I wonder if either of them gave a thought about the daughter that they left in someone else's care and never saw again.
Personally, I think the "penpal theory" of why she was visiting someone at the prison seems pretty legit. Most prisons even today don't do the most thorough check with incoming mail, so unless they were scanning every piece of mail, an older man or even a young man in his late teens to early twenties could have easily flown under the radar of having a teenage penpal. That's also assuming she didn't claim she was over the age of eighteen to make herself seem more grown-up. At that age of 14-16, I know I would have totally been sucked into the fantasy of a man I'd never actually met paying attention to me, writing me letters and telling me all about how fantastic and mature I was. This would be even more apparent if her parents weren't in her life or very neglectful. An invitation to visit them in person would have been like catnip. She probably honestly hadn't thought out a plan more than "I'll visit him in person, we'll talk, he'll fall madly in love with me, and make a plan on what to do when he gets out of prison." Teens aren't particularly known for their long-term thinking. If he'd never seen her picture, he may not have put two and two together. Or he did, realized how very bad it would look to be communicating with a young girl, and kept his mouth shut, probably destroying any letters that he might have kept.