Hold on to your chairs... because here you have a quite classical thriller centered around a girl. Hanna (2011) is a weird story, no doubt. And I'm perfectly fine with debating - as in the case of Beasts of the Southern Wild (2012) - if being raised in a way that's alternative to the great majority and puts children in harms way is child abuse. Probably it is. But then again, raising a child on just Cartoon Network and candy could be considered very limiting and severely suboptimal too. Also, Hanna is 16 instead of 6-year-old Hushpuppy. Evolving capacities, people, evolving capacities. And a rather sci-fi narrative. Let's focus on the particular piece of fiction then.
It's eerie to watch it. Especially if you are sensitive to cinematographic violence. And it makes you question social conventions around the way we socialize our children, teaching them what's acceptable and what's not. Completely arbitrary sets of values, of course.
Also, by showing a quite rare narrative (Luc Besson's La Femme Nikita (1990) and Léon: The Professional (1994) come quite close, though), forces you to realize how internalized in this culture are the idea that violence is something that only adult men do. It's weird and doesn't feel right to see the dreamy Saoirse Ronan killing animals and people. It takes a movie like this to get hit by the hard truth that the violence is heavily gendered. Culturally obvious, but tricky still.
A little bonus just for you: the haunting Hanna's theme. You are welcome!