So I got a friend to play with her while I schooled Bustie but Alli had non of it, gave her handler rope burn and prompty came over to join Bustie.
So, we trotted around a little with Alli coming with us then when we walked and gave Bustie a break, Alli turned all evil! She had her ears glued to her head and was trying to bite and rearing up at me and Bustie. (Bustie was great and ingored her and listened to me but she wasn't the problem) And that was even more dangerous than before!
Long story short, Alli will watch Bustie being lunged no problem but flips when I mount and aren't trotting or cantering. I am completely baffeled! She is usually very relaxed and happy for anything to happen... What might she be thinking to cause it and how can I help her calm down??