Are there other horses out with her? If she is by herself, she could be getting lonely, depressed, anxious, or she could be trying to turn you into her herd in addition to place herself higher than you in the pecking order. It is not a good idea to have a one horse herd. It leads to all kinds of emotional trouble for them. If you can't handle another horse, get a miniature, a donkey, or some other four legged companion. Horses are herd animals.
Secondly, keep your daughter far away from this horse at all times. Do not show affection to this horse through petting, treats, or soothing words. She thinks she is boss, and attempting to sooth her is like a servant soothing a queen and further solidifying their inferior position. When she approaches you, judge her behavior. If she seems calm, give her a pat, then push her away. If she seems moody, stomp your feet, spread your arms out wide, yell and scream. Be the top mare. Don't let her out-mare you. If she throws another huge tantrum, first get out of the way, then shriek at her AND I MEAN SHRIEK! Don't be timid. Get her on a lunge line or lead rope and chase her around. Do anything to determine your role as herd leader. And avoid anything that helps her scare you more.