I just began taking riding lessons earlier this summer. I have had 2 miniature horses as pets for the past three years. My husband surprised me with a 1.5 year filly about 2 weeks ago. The first two weeks have been great. She was calm, she let me groom her and do her hooves. The past week she has started biting, hard enough to leave bruises. Saturday I went out into the field and put her on her lead to have her walk around the pasture with me. We made it around one time and then at the start of the second round she started throwing her head and she reared up on me. I let go of the lead because it startled me and so I could back out of the way. I then took the lead again and had her walk with me to the gate. Yesterday I groomed her and then tried to do her hooves. She did not let me. I decided to wait to do her hooves because she had just came in from being chased around the field by my dominant mini. Today, I came home from work and went into the field, put her on the lead, and was trying to lead her to the post so that I could clean her hooves. She kicked me in the back with her front hoof and tried to bite me. When I told her no, she then reared up on me. Again, I let go of the lead. Then when I went back to grab the lead, she would rear up on me. So I unhooked the lead. She would come up to me then try to bite me. I would tell her to quit. I tried just standing by the fence, but then she started running toward me and rearing up at me. I then climbed under the fence to get out of the field. I know that I have messed up because she does not see me as the boss mare. What can I do to correct this behavior?