Now knowing that Hiroko was, well, traumatised into acting the way she does, it's only relatable. Our past influences our actions in the current much more deeply than those who don't know it could ever realise. As someone who's dealing with that - Hiroko being a fucking dumbass makes sense.
Is it any less frustrating? No. Does it redeem her fully? Also no, because she's clearly unable to communicate well. But it does clear her up and make the story more interesting going forwards.
I'm still sad for Risa.