I also second iridehorses. She is associating the halter with work and anticipates you making her work every time she sees you with the halter. Change it up a bit. As iridehorses said, walk around with the halter with no intentions of catching her, just pet her, give her treats etc. Also, say you do catch her, don't worry about working, just bring her in, groom her, spend some time with her, or even walk her around to graze on some fresh grass for a bit. Good luck dear!!!