I to would not recommend leaving halters on, I would rather see you not turn her out until she is more managable. But, you could try getting a neck band. The broodmares on the breeding farms wear these as identification markers, They normally have numbers on them making it easy to tell one from the other in a large group. But they break easy if need be. Most are made of a plastic you can catch the mare the same as if she had a halter on. I use to catch mares out in the pastures and lead them in by their neck bands. I don't like coaxing horses with treats, but you could use bucket of grain when it is time to pull them in. I would also not feed them any grain in the pasture that way if you do use this method they will come. Personally, I had a mare that just didn't want to come in, in the evenings when it was feeding time, especially if there were horses still out in the pasture (at the time I was boarding, you did full care on your horse no one did it for you) So (try it when you have time on a weekend) I chose to wait till all the other horses were in and she was looking for them, I waited about a half hour after the last horse was taken in before I went to get her. By this time she was pacing the fence near the barns wanting to go in. Then during the week I just went to feed later in the evening when I knew all the other horses were put up before I went out and got her. It took about a week and finally she was waiting or would come up to the gate when I got there. If your horse is turned out with others make her the first out and let her be by herself for a little bit and let her be the last in. Since they are herd animals they don't like to be left behind. Also doing round pen work and developing a better relationship will help. I also worked on this with my mare during the same time. Hope this helps.