I've been imagining everyone at Collinwood gradually one by one finding themselves getting misty-eyed about the old blarney-spiller, leading up to one cathartic moment they all reach simultaneously in the Drawing Room together, where they suddenly all blubber uncontrollable and fall into each others' arms and weep convulsively, spitting up various small expendable organs onto the expensive carpeting. "JASON!!!! JASON!!!!!!"
I think there are probably as many different kinds of murderesses and murderers as there are murderers/esses. Well, no, most are just thugs, but for the others, including society types, each handles it in his own way. Most rationalize or just sort of "swallow" it I would suppose. Millions of people have done horrible things but have just moved on, stiffening inside but not showing it externally except to family at key moments of stress. My father was like that. I speak of him in the past tense even though he's probably still alive.
ECS never really rationalized, not completely, since she felt so guilty about it all those years. It was an open wound to some extent. Her mood would inevitably lighten after Jason, which it did, but she would retain the demeanor she's grown into over the decades. Plus, I think she wouldn't just change back to some light-hearted guilt-free person specifically because this is television. They can't (or think they can't) fundamentally change a major character. We always saw her as reserved and private, and now we know why.
It may take her a long time to get used to a new identity, that of non-murderer. You don't shift gears at fifty so easily, if at all.