:think: So, I have a 7 y/o draft cross mare that anyone can ride in the ring. Beginner to advanced can get this mare to w/t in the ring. Yesterday i was doing hill work with her to "fix" a pulled stifle. My horse tires pretty quickly and I put my sister (she knows the basics of riding and is a VERY confident beginner) on her for the last 5 minutes of her 20 minute workout. My sister made it up the hill just fine but coming down my horse bucked and started bolting towards the field fence where my sister fell/jumped off. My question is why would my horse do this? she was fine for me on a very very loose rein for the first 15 minutes and the second my sister gets on her she acts like she has never been rode in a field. Thanks for the help in advance.