Your mare sounds like she may be in season. Thats not the main
issue. Here is what I do. I never go after or chase my horses. They love to play games ! You are either a game piece to them or dinner comming. I have ten mares in one pasture. when they have foals they are even more suspicious of you. Walk in, sit on a five gallon bucket, let them, come to you. Most of the time I have sliced apples or carrots, or horse cookies in my pocket. Always a brush too. I always give them happiness and pleasure FIRST, before I catch, worm, or vaccinate anyone. Remember, safety first. Horses are jeaoulous of each other and the love you are bringing. Know who your dominant horses are, they are usually the ones who come first and run the others away. They want all the love and food. I have so many, I have to get the dominant ones out of the way so I can spend time with the lessor dominant ones. I place my lead rope under my shirt, place it arround the neck of the dominant mare and tie her away or stall her , so I can catch the one I want. It takes time and patience. I dont know everything , but, this has worked for me for years. The longer you have them, the more they trust you.