I defeated Vierna Da`Sheer a long time ago, maybe 2-3 months or so? But a day or two after I defeated them Jinxie started to say that I have to defeat them again. (It didn't matter to me at the time)

But next week I don't want to have to go and defeat them again in order to move on to the Orchid...

She'll continue to say this until the new zone has opened. Its not require to beat the dungeon to move on into the zone, at least that's what it said in the update about whats up with the new area. You just need to of beaten Aryth's spire. Not only that But I think Dungeons are optional, When i beat the first region the 2nd region had already opened up to me.

Yeah, the dungeons are an optional part of the story line. I remember in the first area Jinxie told me I could either go to the dungeon or continue on to the forest (and I grinded quite a few levels in the forest before I went to beat the dungeon because man Talon kicked my tush)