It’s perfectly feasible that while N was listening into the teams meeting she had her phone placed on the bench, P said she often used loudspeaker. She had it in mute and with camera off too, like many do, and as she listened she most likely would have have had the dog off the lead and was possibly throwing sticks for her to round around.
iMO she could have thrown a stick which went almost to the river’s edge, W went to get it and she feared she might jump in and didn’t want her to so dashed down to pull her up by her harness. That sloping bank is wet and slippery and filled with hard long stars of corn type weeds which are rough as hell. It’s so easy to trip over one and IMO she she fell possibly headfirst into the river then fried to grab W’s harness to pull herself up. The harness slipped off in the struggle and that‘s why it was found where it was.
She then panicked as she couldn’t get out the river ( divers have said how difficult it would be) and tragically she got swept under or along. The other problem is that she was wearing dark blue and black clothes which were the same colour as the water, so unless someone was actually looking she wouldn’t have been noticed. The other problem is that air pockets may formed between her gillet and jacket making her buoyant enough to be swept over through the tidal flow and over the weir. Eventually she would have sunk, obviously.
The biggest sign that she disappeared at that spot is that the harness was so close to the river and the dog was running between the bench where her scent was strongest and between the gate trying to get help without knowing how to as it’s a dog.
Thats my IMO and I think tragically she may resurface in the sea or further down river. I wish I could believe all these other theories but I haven’t read one that is logical IMO.