Answer

By Your Horse

Kicking is indeed a bad habit, especially if it’s ‘hard wired’ into your horse’s brain. You need to make her feel more secure and at ease in the world.
Check her hormone levels – occasionally, mares become oversensitive, flighty or defensive because of hormone imbalance.
Your horse is probably uneasy around other horses or people when her freedom is restricted, and the behaviour is triggered when her anxiety levels rise. She defends herself the only way she knows how.
Punishment is futile and counter-productive. She needs to learn there’s nothing to fear.
Horses have ‘comfort zones’ where they’re happy for us to be – you need to get her accepting you at close range:
1. Hold her loosely with a lead rope over your arm in a small area (bigger than a stable) – don’t tie her up, it could make her anxious.
2. Stroke her from the shoulder, using long. gentle strokes. See if she relaxes under your touch, perhaps lowering her head or breathing more freely. Do not attempt to go near her hindquarters yet.
3. Stroke her head, neck, shoulders and front half of her ribs,  then stroke further back towards her stifle. Be patient and calm.
4. There will be a specific place on her body where she tenses up. Make a mental note of it and retreat to a place where she relaxes again. Then advance and retreat near this line, and gradually the area you can stroke will enlarge.
5. Before you head down the hindquarters and back legs, accustom her to being stroked with a stick over parts where she feels least resistant. Use the stick as an extension of your arm. When you feel ready, go down the back legs.
6. If she kicks out take no notice, just keep soothing her with your voice and stroking until you can stroke a little way down without the leg lifting. Then stop and rest her. Chill out time is a must to take the pressure off.
Over time you’ll be able to stroke down the hindlegs and perhaps lift the tail a little. Monitor her body language. Expect this to take a few weeks. Always stay as far forward by her shoulder as possible, and wear a hard hat.
Once she can accept the stick, your hand will be the next step. Also, allow a rope to swing round her leg, near the hock. Again, expect this to take many sessions and progress slowly until you feel she is familiar with this sensation of the rope.
Project an air of confidence and calmness with slow and deliberate movements.