Board Thread:Spoilers!/@comment-25926288-20170727123737/@comment-30389283-20170727133815

CoolDudeAl wrote: Yep, this is definitly a possiblility. Some also pointed out that she could also take the role of Mother Gothel for the Rapunzel story, although I could see that being a seperate character as well. Of course, first they have to cast NEW Rapunzel. I think Rapunzel will be the other stepsister (and thus, Tremaine is also Mother Gothel), but I think they'll wait 'till the second half of the season for this reveal. After all, the clue was clear in the poster.

Anyway, I didn't know about the character of the Duchess but after reading about her, I think there's definitely a possibility that Lady Tremaine is actually her.