I thought perhaps thrown off the bridge too, however with all the rain, its quite possible that she has 'floated' down the river... so maybe was thrown off another bridge.... which is something they will have difficulty proving. Perhaps as she has fallen the long distance and died on impact. But then there would have to be signs on the body from the impact. Drowning won't show signs, unless marks on her body from the force in holding her down.... and because she was submerged in water for many days, that will lose the trace of being able to use water in the lungs etc, as a point.
Drowning won't show signs, but there would be signs of the fall. It's quite a long way up and her body would have been bruised.
I think he put her upstream and when the rain hit us it has brought her body down to the bridge.