Yes, they like to be up higher than you, but you shouldn't let them. They need to know that you are in charge, not them. You really need to be careful with your face, one bite by mistake can do serious damage. Many members don't allow their greys on their shoulders, but others do. It is a privilege they should earn only when they are behaving while there.
Be careful how you say NO NO NO, it sounds like it would be fun for her to hear, maybe just a stern "No, followed by her name, I say, "No Talon, no heads" and put her elsewhere, I don't say it too sternly, as they like the influctuations in your words, it's fun for them to hear, and it could become a game.
I'm sure others will offer different advice, just be consistent, and do what you feel will work for you.