Just to pile on the comfort issue, it should be obvious that an airplane cabin might be reasonably "comfortable" at one moment, but with a less-than-ideal air conditioning system, that comfort level will change rapidly once you stuff 150+ human beings inside the insulated metal tube.

Perhaps the only reason OP stayed comfortable at all is precisely because the captain stopped boarding.

And again, no excuse for the FA's actions and certainly not a "job well done" IMO.