Firm landing? My response, regardless of the runway conditions, it is necessary to make a firm landing in order to make good contact through the surface water and prevent aqua-planing
One very experienced captain I flew with many years ago said that we all make mistakes, the trick is to reduce the number of mistakes each flight - that goes for SOPs and landings.
As for that passenger's response? Nasty
, rise above it and don't let her very bitter streak affect your self confidence.