Board Thread:Show-Related Questions and Answers/@comment-25974054-20150105192131/@comment-1894786-20150910062505

The Apprentice establishes that Ingrid (AKA Sarah Fisher) didn't come over with either curse, Snow's or Regina's. We know why she wasn't in Regina's, because that was shown to us through "Smash The Mirror". We can assume that she sensed Pan's curse and fled Storybrooke, though how and when is unknown.

When Regina undid her curse, all memories of life in Storybrooke vanished from Ingrid's memory, but not memories of her life in the Enchanted Forest, as shown with Ursula and Cruella (if the erasing of Storybooke wiped the knowledge of magic from everyone's minds, then Regina and Henry breaking the Curse in Storybrooke wouldn't restore those memories for individuals outside of Storybrooke).

Retaining her memories as Princess Ingrid and likely having the Apprentice's scroll still on her posession, Ingrid walked around the Maine woods for a year, trying to find the town, eventually being engulfed by its magical arrival much like Kurt and Owen did in the 1980's. When the Curse was broken, her memories were returned.