It warms my head to hear stories like this! Good job of her father and the bystanders
The only thing I can complain about is going "straight down as a pin". Of course jumping into "unknown" water is a calculated risk you're glad to accept at the time. The biggest risk is that you can impale yourself on nasties sticking up from the bottom (old rebar iron, poles and stuff). You'd want to curl up and stop the downward momentum as soon as possible.
Unless you hit something solid on your way down or just under the waterline, a 20 feet fall into water is not anywhere dangerous. Painful, yes, but not dangerous. But she could easily have drifted under a structure or stayed below the surface, making it hard for her dad to find her in time. THAT would be heart breaking. You've only got a couple of minutes before a drowning person starts dying, so if you loose sight of her you've probably lost her for good. Spotting something below surface in murky river water is not easy.
The cold? Very uncomfortable, but not deadly in the time frame we're talking about. You've got a window of a couple of minutes before you're too cold to swim, which is plenty for this successful recovery. If that time window isn't enough, well... warmer water and prolonged swimming probably wouldn't make a difference anyway.