These are interesting questions. Since it does seem unlikely that she is a victim of random violence, I think we have to consider all forms of non-random violence that haven't specifically been ruled out.
1) I don't think we have enough evidence yet to definitely say she wasn't the victim of some type of kidnapping. Either for money or some other benefit, like attention from someone.
2) She was abducted and killed because someone stands to profit in some way from her being gone. I have no idea how many people that list might include but, since we don't yet have a firm motive, I think we have to consider it.
3) Since she does get out and about, it's also possible that she's unknowingly come to the attention of someone who is mentally ill in some way and obsessed with her just for being her.
What am I missing?