Rainy Hydroplane Rear End

I was driving in a very hard rainstorm and approaching a bunch of cars stopped at a red light (light was ~200m away) when the car in front of me slammed the brakes for a reason I do not know why. I slammed on mine too, and had what would be considered a safe stopping distance with a large gap between the cars. My brakes locked up and I hydroplaned all the way to the car in front of me. Very minor damage to both cars. Mine was the worst of the 2. I know for a standard rear end I am at fault, but does the torrential rain and her slamming the brakes make any difference on at fault percentage or a

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