If you do take your little girl, A., she will really enjoy some of it, and other parts will go over her head.
If she's sensitive, tell her in advance about the Christmas tree that grows, and also about the mice, which are always scary but sometimes funny, too. You may even need to explain what a nutcracker is and why it looks the way it does, with that big mouth and all.
It's essential to tell her the story in advance a few times, so she'll know what is happening and what to look for. People who are used to films and TV sometimes don't know what to do with a story that isn't spoken. That includes grownups!
For the second act, pique her interest by explaining that it's actually a ballet within a ballet, as the court performs for the nutcracker prince and his rescuer. (And it gives the dancers an opportunity to show what they can do!)
She may get a little squirmy and a little distracted, and might want to sit on your lap (such as it is), but she'll probably enjoy being there.
THE NUTCRACKER isn't longer than a movie; it's often the first live ballet a child sees, so you could say it's kid-friendly. When we took our granddaughters to a production here, there were many children there who were even younger than five.
What I'm wondering is how YOU will do. That's a long day.