I recently got a new horse, a mare. She rides fine but has a problem with turning. I'm not a pro horse rider or anything, so maybe I'm the one doing something wrong... Anyway, I try to turn her & all she does is pin her ears & back up a couple steps. And also, sometimes when I'm just regularly riding straight, she randomly turns around to face the opposite direction and stops. After this happens she won't move, & when I kick her & smooch her, she pins her ears & bucks a little. Is this just because she's stubborn?