Copying a response I posted in Ayla's diary
I guess Ayla isn't scared of any other piece of cloth you have on you, like for example your jacket, is she? If not, you could ask yourself what you are doing differently with the halter. Probably, whereas any other piece of cloth is something you are just carrying around for yourself, the halter is something you are trying to impose on her. If that is the case, I would simply treat the halter like any other thing first: just hold it in your hand while interacting with her, or tie it to your belt, but don't try to move it towards her or put it on. Your mindset needs to be clear in that the halter is yours, not hers.
Once it is completely normal for her that the halter is on you while you are interacting, I would start playing around with the halter. But then again, this is something you do for yourself, not in relation to her. As Ayla is a curious little princess, she will probably start wondering what that interesting thing might be... after all it obviously fascinates you so that you are playing with it instead of attending to her. If she starts looking at it and trying to sniff it, I would even make a step back, as if you did not want her to touch it. Simply give her a reward for nothing in particular and continue playing with the halter. When she gets even more interested, you can present the halter to her, but just shortly and then immediately take it back and continue playing with it. The more scarce the halter is, the more interesting it will become for her. In that way, the message you are giving to her is not that you want to put it on her but that she is allowed to join in in your play, if she really, really wants to.
While playing with the halter together, you can move it (again not in order to bring it towards her but just because you are moving it for yourself), and accidentally touch Ayla with it. Just briefly, and then take it back. I would not wait with that until she gets uncomfortable but do it before she can even think of it. In that way, she won't even get to the point where she can find it scary.
In terms of your attitude, I would focus on the following things: The halter is yours, not hers. It's your favourite toy, and you only bring it to the pasture because you want to have it with you. Have you ever noticed how horses always seem to want to eat people's mobile phones or cameras? I think that's exactly because people treat these objects like this: They use them for themselves without attending to the horse, and if anything, they try to keep the horses away from these objects. This creates that magic draw, and of course the same can be done with a halter.