I saw it yesterday too, and think the plan to watch it at home with her is best. Pity it's going to be a year before the second part comes out otherwise I'd say leave it until she can watch both parts together.
Snorting at the concept of letting kids watch fantasy movies about outer space, super-powered mutants, Norse gods, talking raccoons and space/time portals, making them grow up too early. The real danger is that they may not grow up at all because the fantasy world is so much more appealing. Just FGS keep them away from the news...