I'm thinking of showing my 11-year old niece the movie Saving Private Ryan
Don't you think that movie is too violent?
She is 11 years old. She knows what is about.
She may know what it is about but she is still too young. The movie has lots of gore and blood in it which is too mature for an 11 year old.
I think she is mature enough. I won't show it to her if I get a bad vibe from her on seeing the movie.
I can understand why you want her to see a great film, but she probably is too young for all of that violence. You should ask her first if she wants to see it, and if she has any doubts, just find something else that you can both enjoy, together.