1. Good question, but perhaps it was never brought up? (Or I could be completely off base with this theory)
2. I thought that was the case at first, but it recently came to light that she was Asperger's, and where that does not explain or excuse it totally it does allow us to understand her better.
3. I can not speak for the OP but I would imagine that they have done some checking into, but even as the OP has stated LE has been slow in releasing info to them.
4. I do not know Jenna, so I can not say that her friends were/are taking advantage of her, I can only speak from what I have seen from my friend. To answer the second part of the question, yes, a month ago, they convinced her to get a payday loan (~$200), she went to Walmart and bought a $70 TV and had ~$20 cash left on her person, when asked where did the rest of the money she got go, she shut down and refused to talk except to say that her she did not give her friend any money (which I find very hard to believe because one of her friends drives a taxi for a living)
What I was attempting to point out was that a person, like Jenna, who has a mental disorder can more easily be taken advantage of because of A) they want to fit in and feel 'normal' and B) they don't realize that they are being taken advantage of. The reason I was using the 'friends' was to say that they may or may not be true friends, based on my observation of my friend.