Mare threatening to kick when being caught
My seven and a half year old Appy Sport horse mare has developed a disturbing habit. She has suddenly started to threaten to kick, swinging her but towards anyone who's holding a halter when approached with a halter. This started recently, a few months ago. The first time was when we wanted to catch her for the dentist, her teeth had been floated three months ago, but needed cleaning. She was in her stable camp - my stables have a little camp in front about the same size as the stable. She decided she didn't want to see the dentist and threatened to kick the worker who went to catch her. I immediately went over, caught her with little fuss.
Since then we've had a bit of trouble catching her, but nothing too serious. Then Yesterday the horses were brought down from the hills for work today. She had a bunch of burrs in her coat and tail so I walked over while she was loose and started picking them out. No fuss, told one of my workers to bring me a halter to take her somewhere I can remove the burrs from her tail in peace - we're surrounded by 9 other horses who all want their share of attention. The moment she sees that halter all hell broke loose! She tried to avoid us at any cost and when cornered she swung her butt towards us.
She has no reason to have negative association with being caught, she is not a regular work horse, so being caught doesn't neccesarily mean work.
I know whe probably should have had us one of THOSE meatings right there, but I needed to get the other horses checked over, brushed out (shedding out winter coats) and tack put out. She was caught by the workers while I was catching another horse they were having trouble with, brushed out and released. We have never left her alone if she threatened to kick so no reward there.
What can I do to fix this waywards horse?