ONTD

This is what I wanted. In fact, at first, I thought that's what happened. I thought she'd had a change of heart and stabbed Cora in the back because she realized that she could never make amends/get Henry back/find her happy ending helping her mother do something like this. It was bittersweet to realize that she'd fallen for Snow's subterfuge because it's two steps back for her character.
She's still doing things to gain approval for other people, rather than as a result of a genuine change of heart. In order for her to be seen as different, that has to change.

Agreed on the underhandedness. I get that Regina has done this for years and years to Snow and those around her, but isn't the point supposed to be that Good (TM) is different. I know Snow regrets it, but regretting it doesn't change the fact that now Regina has a genuine reason to be upset. I think Regina would have been furious if Snow had killed her mother outright, but the fact that she made Regina a party to it will make her wrath that much stronger.

TL;DR Yes, this.