I disagree. I wouldn’t assumed she had bad news on the call and needed to walk away. Have you never felt like just walking away? Sometimes we need a break and a breather, and then come back.
same with the dog being tied up, if I walked my dog in a field and saw another tied to a bench, I’d just assume the owner was nearby, maybe in a bush having a wee or something silly like that. I wouldn’t admittedly think it’s been abandoned and anything sinister.
there’s no scuffle, no sign of a fight, no sign of her in the river, so not automatically a police investigation