The accepted terminology for a person approaching the teenage years is "tween." I think a more descriptive word is "preen." That's what we use for Miss A, who is eleven. She is a delightful person, and I have every hope that we will pass the hormonal storms of adolescence with minimal damage. But, of course, we have our share of preen snark. Here I will post a collection of B and I's terms and definitions as we enter this new stage of life...
The Moo of Displeasure: n. Sound given by the preen when she is told she must do something she does not want to do.
The Noncommittal Yak Humph: n. Sound given by the preen when asked for an opinion on something she cares nothing about because she is absorbed in what is vitally important at the moment to her.