Board Thread:Show-Related Questions and Answers/@comment-5344051-20160229080952/@comment-25536775-20170501200033

8Rob wrote: But it was said several times that there was no way to escape the Dark Curse

Maleficent said it when the Fillers of Darkness asked for help in 4x13 (I think)

Even more, if they could escape the Dark Curse just like that, Maleficent didn't need Snow/Charming's help in 4B and Cora's shield was pointless. They only needed to teleport themselves somewhere else, out of the curse radius. The Dark Curse had never been cast by anyone before; no one except Rumpel would be fully knowledgeable on what its effects were. And Rumpel's only had four students that we know of: Cora, Regina, Zelena, and Trish.

Maleficent simply didn't know that the Curse would only reach a small fraction of FTL. Cora probably didn't know the full effects of the curse (And that's why she cast the essentially pointless time bubble).