A suggestion, someone said to get off when she kicks out when undersaddle and then lunge her. I would not get off, and instead just really work her while you are on her to let her know it is not acceptable behavior. By getting off, even though she is getting worked, she is going to associate "oh if I kick out then my rider gets off." So if you feel you have the experience to sit it out that would be the best thing.
I suggested the getting off and lunging until she is over her kicking spell mainly because I was getting the idea the OP was not a really experienced rider and I was worried more about the fact that the horse may knock the rider off and step/kick the rider and if she is on the lunge line the rider hopefully will be able to see a kick coming and this way he/she is out of her kicking range.
You know how to make a miniature horse even smaller? Leave them in the dryer a little longer!
"Don't ever regret something that once made you smile"