This is pretty much exactly what my Sunny and I have struggled, and STILL struggle with sometimes! What I found that helped a lot, was a ton of flatwork that incorporated poles and small jumps. Going over poles should be a non issue, you should be able to flat over them like they aren't even there. Then start to do it with the tiniest crossrail, and slowly make it larger as she gets better. And do some of this in every ride, and she'll eventually realize it's not a big deal, the jumps don't have to be big, it's not like you're jumping her hard every ride, just cantering over small obstacles. You can make a whole little jump "course" with poles on the ground, that's great practice as well without actually jumping height.
I would only jump my Sunny every once in awhile because she would get so wound up, and she knows her job, but I didn't think that I needed to jump her very often. WRONG!! It's only when we started doing a lot of jumping, and not big stuff either, that she got better. When you only jump once in awhile, it's like a party, the horse likes it and gets so excited and wound up and you can't get anything accomplished. Once you start doing a bit of it all the time, the novelty wears off and then they settle down, go to work and you can actually make some progress.
I love the jumps on a circle exercise, for me it's just thinking about lots of inside rein and outside leg, and lots of bend to keep Sunny soft and paying attention to what we're doing. And I keep a feel on her mouth over the jump, and nice following hand and a slightly open rein to keep her going around on the circle, I don't give a big loopy release because horses like consistency, a more erratic horse, (like our Sunny's!) need that soft quiet consistent feel for them to become quieter. They'd rather you have a nice soft following hand all the time rather than throwing the contact away and then having to snatch it all back up on the landing. If Sunny's fighting or rushing or being a **** I don't let her jump like that, I circle her away, reestablish everything and then come again. She doesn't get to just be a crazy horse anymore, it was a huge production at first and you bet she fought and bolted and bucked and protested, but now that I've been insisting that we're going to do things quietly and am super consistent in my body and my contact, she has gotten TONS better over the course of just a few rides. You just have to be super consistent! And your Sunny is super young still, so you have lots of time to improve and get it right:)
Putting poles in the middle of the arena and doing serpentines over them is also really good to work on corners, bending and balance. The book 101 Jumping Exercises for Horse and Rider is excellent for getting ideas as well, basically any sort of grid can be done just with poles on the ground, the sky is the limit there, haha.
I hope this stuff helps:) I didn't know you had a blog! I'm going to check it out when I get home, it's blocked at work here, haha.