Biting you should not be acceptable AT ALL. I would give her a closed fist to the nose. The offending appendage is the one that should be punished, to quote a friend. She will learn very quickly it isn't acceptable.
I agree with most of the opinions expressed here, except the one above.
I own a biter. My experience in trying to rehabilitate my horse is exactly the opposite as stated above; hitting your horse is meeting aggression with aggression, ingraining more negative experiences into the animal than those that he already endured.
A biter developed his habit as a defense mechanism against any thing unpleasant, including US. Carrying on hitting will just perpetuate a full circle with no good results. He might refrain himself from biting, but just caused by fear, I can assure you that should the opportunity rise, he would bite, perhaps even harder.
My horse tries his best to intimidate with we fasten his girth. He has bit before in more than one occasion. Reason: simply he was bored of being ridden, hated his work, his saddling (synonim for work). My strategy has been:
- Check if she is girth sore, buy a girth protector like Prolite or Nummed.
- Show her the saddle before saddling, let her smell it;
- She might be girth ticklish; massage her girth area (TTouch) prior to saddling;
- Keep her lead line short, avoiding her teeth to get hold of you;
- Put the briddle on first, that way her mouth is full, not so free to bite;
- fast the girth gradually, hole by hole, with time elapsing in-between;
- Give her plenty of praise;
- Walk her a bit in circles before you fasten the last hole;
- Kelly Marks also suggested that as she tries to bite, you kick gently her hoof with the tip of your foot; she won't know what caused it and won't relate it to you, as you were busy doing her girth; next time she think twice whether biting was a good idea or not.
A biter is a very special horse. He needs plenty of patience and self-control on our behalf. It's far too easy just to lash out, isn't it?!
P.S. By the way, biters used to get wacked across their noses easily become haed-shy.