Often think the most boring explanation is the one that's probably right. The dog has probably got free from the harness or gone too near the river, she's gone to retrieve it from the water's edge and put the lead back on. At some point she's slipped and fallen in, and if the river's moving quickly then that's it.
When I was 8/9 years old and learning to ride a bike, I was cycling along the Mersey down by Burnage Rugby Club, just before you hit Parrs Wood. Took one hand off the handlebars and went down the bank straight into the river. My parents were there so they fished me out, but if I was on my own I'd have been fucked.
I never made a noise. It took 3/4 seconds to even realise what was happening, then once I hit the water I lost sense of myself. Thankfully it was a dry summer day so the water was slow and fairly shallow, because when it rains heavily the water comes right up to the banks and moves quickly. Could have easily been a goner.
Like I said, my dad fished me out and the worst that happened was I got a really nasty stomach bug from swallowing half the river (made the mistake of going to a City-Arsenal game the next day, the one where Lauren scored that really bizarre own goal, and missed half the game), but any colder/wetter and who knows.
Her poor family. Especially her daughters. There's nobody like mum in the whole universe.
(If anyone wants to see where I cycled in:
https://www.google.com/maps/@53.4071619,-2.21261,3a,75y,109.7h,95.18t/data=!3m8!1e1!3m6!1sAF1QipP42YI5YGUHEm201nsKJ6GimheySWBcNVg_FuYq!2e10!3e11!6shttps://lh5.googleusercontent.com/p/AF1QipP42YI5YGUHEm201nsKJ6GimheySWBcNVg_FuYq=w203-h100-k-no-pi-0-ya315.37378-ro0-fo100!7i8704!8i4352)
