I took her friend's comment about not being in the right state of mind to mean she was inebriated and not safe to drive. I wonder if there was any discussion or disagreement then about her driving home? Did someone nearby see her stumbling toward her car, for instance, and offer to drive her instead? It could have been another party goer that she did or did not know.
When the friend says she was planning to stay the night, I wonder if that means just sleeping in her car or if they had a set up with tents, sleeping bags, etc. How many other teens spent the night vs leaving and going home? Was the party kind of winding down/breaking apart when Kiely left or still in full swing?
I also am not convinced she was abducted; I think there's a good chance that if she drove home, especially inebriated, she may have had a tragic accident and not been found yet. Very sad either way and I hope she is found and her family can get closure, hopefully with a happy ending, but either way.