Addressing the speculations about Tamara possibly being connected to an existing storybook or fairytale character, such as Wendy, the way Mitovich has commented on her character and dropped his spoiler hints about her suggests, at least to me, that speculation on that front might not have much, if any, validity to it.
I could be completely wrong, but I haven't gotten the vibe - based on the way he's commented on Tamara's character - that the writers are connecting her to an existing fairytale or storybook character.
Having said that, however, there is one existing character that she does kind of remind me of, at least in terms of what we've seen of her role thus far: Lord Ombra, the primary antagonist of the Peter Pan prequel/reimagining Starcatcher books.
Evidently, there is a Disney character called "Tamara." I didn't know of her because I haven't bothered too much with Pirates of the Caribbean.
She's a mermaid and according to the link, also called The Mermaid Queen. Ursula, anyone? Skin color and features aren't the same, but...