She seems a bit 'behind the hock,' which means that her cannon bone is angled away from the hock. But it is in shadow, so I may be wrong. Her hindquarters are high and she has a short back and high withers, but as she's only three, nothing can be entirely for sure, as she's still growing.
Remember that her conformation will reflect on her abilities, and when she can begin more intensive training. Contacting a professional is always advised, as you can damage a horse's legs by working them too hard too early. Particularly in jumpers.
When training to jump, I always advise people to make sure there is a bond of trust between you. Jumping is dangerous, and horses are dangerous. Combining the two is especially dangerous, and you need to make sure that your horse trusts you over its natural instinct (which may be to run, refuse or rear).