Tell her what you think and feel. Be adult about it. I have found few things in life that are as impressive as a child that speaks intelligently, like an adult, to get their point across. Quite frankly, it blew me away when it happened to me once. I didn't know what to say.
Adults expect children to be children.
If you want to show her you are not, then show her. She'll never listen if you start whining. I am sure that you can come up with something. Just impress her with your maturity. If you can't, then perhaps you are not yet ready to gain that promotion to adulthood.