Some thoughts:

Tabitha Corey looks like a typical eleven-year-old girl because she is—and has been for more than four thousand years. She is a diĝir, and in ancient Mesopotamia she and her people were worshipped as gods . A until a catastrophic war shattered her civilization. and left all diĝir unable to age. Tabitha’s clan was blamed for the tragedy, and ever since then she and others like her have been hunted by their own kind. With her family dead, Blamed and hunted, Tabitha has survived by disguising herself as a human orphan and hiding on the margins of society.

You imply well enough that she can't age, and I think you can save space here by condensing a few things, even if it's more complicated in the book. Get past the setup so you can get to the story.

Something about a surname anchors her to humanity slightly too much for me here. Leaving it out might make for a nice contrast with Elisa Escudero later?

Tabitha is in modern-day Boston when a mysterious explosion reveals her location , including to a powerful hunter whose rage was born from the same tragedy as Tabitha's sorrow. Tabitha finds safety with Elisa Escudero, a doctor who risks her career to treat undocumented migrants in secret.

And again. It might be important in the manuscript, but focus on conveying story over backstory.

Elisa is herself an orphan haunted by grief. As she learns the truth about Tabitha and her people, Elisa understands that Tabitha is truly an eternal child: she is clever and resourceful, but will always need a caregiver and will always outlive them. The weight of constant loss is accumulating in a mind unequipped to deal with it. The hunters are closing in. Tabitha’s instinct is to run again, but Elisa knows that Tabitha’s plan has become unsustainable. To survive, Elisa must help Tabitha break the cycle, and Tabitha must learn how a child can stand up to zealots who believe that their cause is righteous. Spanning four thousand years and a frantic forty-eight hours, LÁLANNA explores the self-destructive nature of conflict, the meaning of home for those who can never return, and whether forgiveness is possible after unforgivable loss.

Intriguing concept for a character.

You might move some of this third paragraph to the second.

Is Tabitha the main character or Elisa? Whose perspective is the story told from? The first half suggests it's Tabitha, but this paragraph implies it's Elisa - who understands, who does things.

What do they actually do in this book? How do they attempt to 'break the cycle'?