I've been leasing this horse for 6 months now, a 26 year old Morgan mare she's never been the best horse to mount. At first, she would just walk off once I got on her but I fixed this. She was good mounting for a month or two, then she started swinging her hips away from the mounting block. She did this one or two times, then stood quietly so I just thought she was playing games. When I mounted slowly, she would stand perfectly still. But yesterday, she swung her hips away for about a half hour, since I only ride for about 30 minutes anyways (because of her age) I ran out of time and I couldn't ride. I tried to keep her head bent towards me, but that would just make her swing her hips out even more. Then I tried walking her around the mounting block a few times. This worked, but the second I pit my foot in the stirrup she would swing her hips away. What should I do?