Last week, we were talking here about what Gracie's backstory will be. One one hand, we want hers to be as powerful as her sister's, but on the other we can't wish the same pain on her.
I could be wrong but to be honest, I don't think Gracie's backstory is gonna be as bad or painful as Luna's backstory.
Hopes said before that other characters' stories or backstories may get dark, but will not be as dark as My name is Luna,
Also, to add, this is just my personal feeling regarding it but I think putting not just one but both DeLuca girls with same level of trauma does feel like overkill.
My possible theory on what happened to Gracie in the forest:
Child Gracie and Luna were exploring the forest despite warnings from Cordia and Wilfred to not leave the house. While exploring, Gracie gets separated from Luna and lost.
Gracie calls out Luna and in the process, awakens a bear nearby which is angry.
The bear attacks Gracie angrily and Gracie suffers her blackout due to fear etc.
By the time Luna and rest of the Family soldiers find Gracie, they find her covered in blood (not hers, but the bear's), and the bear slumped, dead already.
Luna takes Gracie home, and on the way, Gracie wakes up from her trance-like state, wondering what just happened.
Obviously, above scenario is nowhere near as tragic or sad as Luna's imprisonment with the Mysterious 6, but amping up the fear factor with child Gracie being stranded in the woods as well as having to face a bear alone by herself can present a different type of trauma for her that I'd be interested in.