I understand you want to move on, but you said she's been more or less a pasture ornament from the ages of 6 to 15. That doesn't equate to 15 years of solid wp. Sounds more like a clean slate to me.
Anebel & Spider & I (though I am not nearly as into it as they are) are tyring to say that you can't really move on into any of the 'moves' until you get the basic foundation down solid. You can't rush it. Even if you don't plan on competeing, it's a case of you need to do it right to give her the benefits of dressage. It's not a knock, but it's what's best for her conditioning.
Anebel - I was refering to the comment about her horse not being able to carry her neck in that manner. I know it's more about the whole body, training & control of movements. But, from someone who rides almost strictly QH's a few dressage people in my area can be kind of snooty about the breed and make remarks about how my horse shouldn't DO that. ;)