I guess you're talking about this picture.
By looking at facial features, she appears to be Mullin's daughter, Annabelle, with a side braid tied at the end.
You might be confusing the color of her hair with black due to the dark background color.
So it's not Annabelle, and when she moves the portrait the eyes of the girl get lighted up, like if she was possessed, but, this in theory would be happening before the creation of the first doll, kind of contradicts the plot since the doll becomes possessed after the parents make a deal with the devil and that happens after Annabelle dies.
Well, the devil was in that doll as plot mentioned. If you remember, that doll was made before their daughter died.
As Esther said,
We knew it was her.
She wanted permission
to move into the doll...
...so she could be with us forever.
We said "yes,"
and that's when it became stronger.
However, devil was released from that room when Janice, the girl who found this portrait, opens doors of cupboard where that doll was kept.
And we have seen him running around freely and possessing Janice.
In horror movies, devils are shown to possess anything such as that Zoetrope toy in The Conjuring 2. It doesn't matter when this thing they possess are made. And also it wasn't their daughter at all that they used to see glimpse of. It was that devil.
As said by Esther,
...it was comforting just to have
the buzz of activity again.
But we soon realized
it wasn't our Annabelle at all.
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