"True," Archie said, "but she's also the only blood family Regina has left regardless of everything else she's done. Regina might want to give her a second chance despite all that because Cora helped ruined both their lives."

"Helped" because Regina and Zelena had both made bad choices without their mother's direct influence. They still could have made better choices once they were no longer under the terrible woman's thumb though it would have been harder than someone who had been raised by good parental figures.

Archie saw a good example of someone who struggled with staying on the right path instead of giving into patterns their awful parents had taught them every time he looked in the mirror.