I'm willing to give the boyfriend the benefit of the doubt, except for one nagging question. Per the Zillow link, the river is maybe 30 strides from the house. If she walked "in the direction of the river", you could see her walk every step of the way from the house. You could easily see if she ended up in the river or not. Maybe he was shocked that she assaulted him and didn't feel like following her, who knows, but that detail is strange.
That's not the main river.
The river closesed to their house was frozen.