I have owned a 14 year old mare for about 5 months now. When I try to back her up she will not. She Stands there. This has become a problem because she will run you over and not back up.. she will run into you to get food and will not back up. Now when I try to use a halter and leadrope to back her up (saying back and tapping her chest with the lead rope) she does not move.. She is good at other stuff. She backs up when I am in the saddle. She is a big horse and I am only 5'1 and 85 pounds. I feel like she could hurt me someday. Please Help me solve this problem.