Just running a wild thought over in my head and sharing. I'm not saying this is what happened, I'm just throwing what little we know up in the air and seeing how it falls.
If we suspend our notions of what is likely for one moment, and accept that someone other than NB could operate her phone then it becomes only an assumption that she herself clicked on the phone link for the teams meeting (camera and audio off). It is possible to send a text on someone else's phone which appears to be from them if they have access to it. The only witness sightings were from a distance (dogs interacted but did they interact?), then the last physical interaction with NB for definite would be dropping the kids off at the school as the kids and teachers/other parents could not be mistaken. Could it be that it was someone other than NB in the field but dressed up in the same clothes, of the same size, same hair, with local knowledge, who would be able to control the dog as they had walked it before? The bench scene then being staged. Whatever happened to NB having happened immediately after the school drop.
Please do tell me if there are obvious holes in this so that I can put it in the discarded list.
I'm still leaning towards a possible abduction, having abandoned the river as a theory.