I've had the same issues with my horse in the 10 months I've owned him, although we rarely jump, these are things I do to loosen him up and get him working properly.
First, if you can I would look into getting a dressage trainer to help with your riding. If you already have a trainer, ask for a break in jumping and really focus on dressage.
The absolute most important thing in dressage is how you ride. If you don't carry yourself correctly, the horse will not carry themselves correctly. If you don't already, try to use your seat, then legs, then reins for all aids. By that I mean try to control your horse with your seat first, then, if you're turning or asking her to move foreword your legs and then reins in a non direct way if possible. Contact should not be with just the reins, you need to have contact with your legs in seat for the horse to move properly. Of course, this is a very general description. Like I said, getting a trainer would be best, if not, read as much as possible about dressage. I strongly suggest this book, http://www.amazon.com/Dressage-Exercises-Horse-Rider-ebook/dp/B003WOL56Y/ref=sr_1_1?s=books&ie=UTF8&qid=1341624733&sr=1-1&keywords=101+dressage+exercises and these sites, for info. Http://www.artofriding.com/school.html http://www.classicaldressage.co.uk/
For my horse, I like doing lot's and lot's of trot poles, riding on hills, figure eight's, serpentines, circles etc. I also do an exercise where I ask my horse to walk freely forewords, move up to slow trot for 5 or 6 strides, then promptly halt and back up for 5 steps. When done correctly, this will cause the horse to round their back and work from their hind end more. These are just some of the things that have helped me, I'm not at all a good rider and dressage with my horse is very much a work in progress, but it has improved.
It would be very helpful to see videos of her so that people on here could critique her properly.