Here’s a quick bit of parallel in the show that I hadn’t thought of before. Don grabs Betty. Betty reacts with a little fire in her eyes, but basically with passivity. Later, Betty slaps Helen.
So can we conclude that Betty was “really” slapping Don when she slapped Helen? A bit of deflected anger?
And then later the conversation with Francine, in which Francine lets off a litany of absolutely deranged reasons to hate Helen Bishop. De. Ranged. Add these two incidents together and it seems like this is who Helen is; a place for the married women to project all their fears, anxieties, and rage.