There is a moment in every horses life, where they take the step from cute adorable and sweet baby, into entitled, pushy teenager. They all go through it, they all try to see if they can take over the situation.
The problem is, up to now they have been sweet, agreeable, and wonderful to work with. They live in a world of new interesting experiences, cookies and scratches. Then one day they decide they deserve to eat now, out of the bucket in your hand instead of waiting politely in their stall.
Then when you say no, and tell them to back up, the ugly teenager surfaces and you get a temper tantrum with a butt turn and kick in the direction of authority. At that moment, you, as the senior partner in this relationship have 2 choices. You can say "No, no." then go ahead and feed the nasty critter, just like she wants. Or you can assert your Alpha mare status, and have what we used to like to call a "come to Jesus" moment with your errant teenager.
This involves immediately yelling, flinging buckets, and chasing the horse out of the barn and away. This should go on for several minutes, convincing the snorting and scrambling teenager that the fire of heaven is about to rain down on them and the ground swallow them up for sassing the boss mare.
Then invite the teenager to be mannerly, walk into her stall, back into the corner and wait for the grain to be poured. If she does it fine, if she argues, back out of the barn she goes. And those ears better be up and perky.
It usually only takes one time, and my teenager followed me to the gate later that night for a goodbye neck scratch (at a careful respectful distance and with ears at attention).
I think I will get one more try from her, she is at the bottom of the pecking order and desperately wants to boss SOMEONE. But all I have to do is enforce that I am Alpha, and we won't have any more rude behavior.
Hopefully next time I won't break a finger though.