My feeling is that by soliciting information about changes in behavior and such they do not have a POI in mind. It could still be someone known to her in some way but maybe they tracked down everyone they could possibly find with a link to her and got nowhere.
I respectfully disagree with this, even though I do get that feeling to some extent/on some days. I find it highly plausible and not too “CSI television drama” to believe that they for what ever the reason they could be leaning strongly in the direction of a certain individual(s)or have a hunch without a lot to go on and just need a final solid piece of something...anything, that’ll help them nail it down and formally name them as a suspect. Wishful thinking on my part perhaps.