Board Thread:General Discussion/@comment-25926288-20160307025112/@comment-24674051-20160311180204

In the 3B finale, we saw Regina finally relishing the destruction of Snow. She caught Snow alone, with her guard down. It was all done by Regina herself. So she could take satisfaction with the deed. And Burning at the Stake is a very painful form of torture and execution, unlike the quick death achieved by crushing a heart.

in SotD, Regina showed a reluctance initially, and I think it may have been because Snow was handed to her by Cora. I don't think she wanted to give her Mom the satisfaction of having given Regina what she wanted. and the heart was only crushed AFTER it was revealed that Jiminy was being totally awkward, and therefore the heart was NOT Snow's.

As for Regina's reluctance (except in 3B finale) i think it may very well stem from the fact that Snow is her StepDaughter, and there is a relationship there. Also, even though Regina publicly blames Snow for Daniel's death, we saw that Henry provided reminders to Regina that it wasn't Snow, but Cora, that was actually to blame.