I just saw that movie and I highly recommend it for adults. When I read the synopsis of the story before I saw it, I thought it might be a depressing story, but somehow after watching it, I found it definitely not the case. It was uplifting as the main protagonist, 6-yr-old Hushpuppy, displays the positive traits of a survivor against all odds.
FWIW, the child actor who played the role of 6-yr-old Hushpuppy was unbelievably good. All the actors used were not trained actors, but that didn't make for an amateurish or create a problem of a roadblock to the storytelling. IMHO, it added to it.
I can't claim to know if a child would enjoy it, frankly. I'm unfamiliar with the age of your child but if she is over about 12 or so it might be entertaining in spots to her/him but possibly not age-appropriate as it's pretty dark and deals with heavy issues of alcoholism, end-of-the-world scenario and illness and/or loss of her closest of kin.