Her head doesn't look too far down, however, you can tell by that picture that the horse goes around lazy. Heavy on the forehand can be a bad habit from poor riding/training, or enforced through riding a horse heavy on the forehand, or can be from just plain laziness.
I look at that picture and the horse's head doesn't concern me. However, she is pushing unevenly, and jumping the rail by just using her left hind leg. She doesn't look forward or enthusiastic, and her front legs are just half-heartedly making their way over the jump.
Regardless of the size fence you jump, or even if you don't jump at all, a horse should always be encourage to use its hind end - it will help infulence everything that you do with the horse. And regardless of the start of the reasons for being on their forehand, the end product is a horse that isn't developed enough in the hind end to get off the forehand. So a bad habit soon turns in to physical inability.
Hill work and half halting are great way to get the horse off the forehand. However, my personal favorite is to do a ton of transitions, and since you jump, I would also do a lot of gymnastics with her.
I had a horse once, a belgian QH cross - he was 15.3 hands, but drafty built, and he had very very large feet. He was clumsy, a little lazy, and he was soooooo heavy on his forehand that he would forge (hit his front heel with his back toes), and even trip himself - he actually fell down one time because he tripped sooooo bad.
Once I found the right trainer to work with me & him, we were encourage to do plenty of transitions - plenty-plenty-plenty. In specific, walk or trot or even canter to a halt to a back to a trot again helped a TON. But twice a week "transition" sessions helped soooo much. Get creative. You can do walk-trot-walk, walk-halt-trot...anything...any combination.
Use in moderation, and have a plan for developing your horse's hind end and ability to lighten up the front end. Do not push the canter gait too much at this beginning stage of working on transitions. Give that a few weeks until the horse gets stronger.
It took my clutzy horse 2 months, and we were able to do halt-canter departs, and in another month, before I even realized it - we could canter nearly in place. It was my first introduction to dressage, and I didn't even know it. I pursued dressage from there and realized how much the training recieved in that discipline affects everything you do with your horse.