Not getting back on the second time is not letting her win. Just make sure those lunging lessons are hard work, don't take it easy on her! Like I said before, when lunging her before you ride her, it will help out with the kicking under saddle also. If she does kick undersaddle I would definitely lunge her but if she continues to kick once you get back on just leave the day with a hard lunging lesson. She will pick it up eventually that kicking=more work and that it does not get her out of work. It takes time and patience, don't expect to see results overnight. These thing take time and lots of patience and understanding.
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"