I have had my mare since October. She is a 5 year old. Me and my trainer started working on her in October and she was doing GREAT for the first month and a half to two months. We had no issues. There was a period of time where my trainer and I were really busy and couldn't come out consistently. In the beginning of December or so she started acting up on the lunge line but we have since corrected that issue.
A couple of weeks ago we got our first good ride in in a while. My trainer rode her first and she did fairly good for her. I got on and she did good for me up until the end. I was going to canter her ONCE more around she she decided to kick out. I backed her all the way around the arena but she continued when I asked for the canter again. My trainer got on her and at the same time Cheyenne was kicking out my trainer made the mistake of pulling out her keys from her coat pocket (they were in the way), which escalated the problem because she spooked a bit (probably thought the keys were to be her punishment for the bad behavior she knew she was doing). My trainer ended up coming off because she bucked. She got back on and tried to settle her a bit.
After that I got on her the next day and she gave an attitude (kicking out) even at the trot. When she goes this I spin her around and keep her going forward. We put out poles and comes to keep her mind on other things besides bucking/kicking. It has to do with putting leg on her. When you put leg on, her ears pin, tail swishes, and usually a buck or kick out follows (that's why I started spinning as soon as the ears come back).
She had another 6 days off and I decided to start back at the basics. I free lunged her, lunged her, and lunged her tied down. Did perfect. As soon as I got on last night (she's fine when you get on, acts perfectly happy) but when I lay my leg on and even ask for a walk, she refuses and gets aggressive. I try to push through it but I'm not sure how far her threats will go. I told my trainer and she said just keep plugging along with it and get what you want. Last night (even though I was scared to death LOL) I got her to walk both directions (she bucked and kicked out probably 10 times).
I don't really understand where this is coming from. Supposedly she has had a history of bucking in the past (talking to the breeders and prior owners). However, she was doing SOOOOOOOOO GOOD for the first two months and then this pops up out of no where.
EDIT: Also, her head is low and where it's supposed to be. There are no other issues except for when I put leg on and ask her to go forward.