getting a halter back on a young filly

Question
My daughter was given a 10 month old filly. 1/2 wild mustang and half saddle horse off the Navajo Reservation. We have had her wearing a halter 24/7 for about a month and a half maybe 2 months. We read that you should not have a halter on your horse 24/7 so we took it off of her for a day. Now she will not let us put it back on. She will startle and run when she sees the halter or lead rope. We can get close enough to pet her when our hands are empty but if she hears the buckle of the halter she turns her back end to you, she has not kicked yet but... We never had any problems before. How do we get the halter back on?

Answer
Dear Jim,
What has me concerned about your letter is not so much the halter situation but that (granted- this is only based on the contents of your letter - so apologies if I am off the target) it seems that your family doesn't seem to be very horse- savvy. A foal is no place to begin horse ownership - even a "free" horse can do significant damage. Very young horses are for very experienced horse people.
Anyway- you are quite correct that a horse should NOT be wearing a halter day and night. While she had it on however- and while she was stalled (or at least in a confined area- the halter should have been put on and taken off over and over again) easy way is to use two halters- so she's never actually "loose."
She is going to have to be de-sensitized and halter broken - simply wearing a halter doesn't mean she was ever halter broken (as you are now all too painfully aware). I would begin by simply having the halter on my arm and go and feed her a treat- DON"T try to put the halter on her- just have it on you. Every time you go to feed or to groom her carry the halter. This will, take a week or so. When she doesn't care about you carrying it anymore- get her into a more confined space - a stall is perfect- but a small pen or corral will do.
Once she is in a smaller area- get a bucket with a bran mash - something that will take her a while to eat. As she is eating - begin to groom her- again with the halter on your arm- let her hear the buckles- make no move to put it on her but do touch it to her body and her shoulder. She may flinch but as soon as she realizes you're not trying to catch her- she should relax. Again- don't try to put it on her. Do this for two days. Then enter with the treat bucket- which by now she should be looking forward to and hold the halter wide so that in order for her to get her head into the bucket she HAS to put her nose into the halter. Be patient and DO NOT try to do up the crown piece. If you have a halter that does not have a crown piece that unbuckles- get a new halter that does. Don't let her has as much as a nibble unless that nose goes into the nose band.
After two days of this go ahead and quietly scratch her ars while she's eating and if her body language tells you she's relaxed enough- softly lay the crown piece over her poll- don't buckle it. Go through this three or four times. Attach a short  (say one foot) piece of cotton lead line to the halter and once she has accepted the crown piece- quietly buckle it very loosely. DO not grab her by the halter- just let her think she's still loose. The short length of lead will give you something to hold onto. Once you have a halter back on her- now's the time to begin the two halter trick that I mentioned at the beginning. Put two halters on her remove one- leave one- just for practice. Make sure throughout the process that you give her lots of gentle face and head handling.
Best wishes,
S. Evans