The following is all MOO and it's burning a whole in my brain...so here it goes...
I believe she was abducted by someone she knew. I believe she was walking and merrily texting back and forth with her "friend/classmate", lovey dovey and all. I believe she was approached via car and asked if she either wanted a ride home or up to her friend's home. Somewhere along the road, and I think sooner rather than later, she was overcome and her phone was taken then shut off. If it was someone she knew well, I am fearful of the outcome. If it was someone she knew either through family or friends, I believe she may be alive still (which may be a fate worse than death).
There are other viable options for her disappearance, I realize. But, for me, this seems the most logical based on what LE has offered up. There's been no indication that AH was into partying or drugs, so skipping off to do something illicit doesn't seem viable. And, through SM, there is absolutely no public info about AH being bullied, so a team of wild girls hurting her seems far fetched. Because the father's role in this case is being mysteriously blocked, I could possibly entertain some weird theory where there was a revenge plot against him.
But, when I think about what sort of scenario makes the most sense, I come back to my original theory, as stated above. IMO, AH was abducted by someone she knew and she needs a miracle to occur to come home.
Again, this is all my own opinion.