The very first thing I noticed is that you need to work on your hands. You definitely need to widen them. It appears as though you're riding in a large roundpen (although correct me if I'm wrong), which means you are essentially riding in one large circle. Ideally, you should be looking into your turns instead of looking straight forward. Also, your outside hand should have more contact in order to support her through your circle, and your inside leg should be used to push her out into your circle. Your inside hand should only be used as a guidance reminder if she is not responding to your other aids. You should never have to have your hands become that uneven by trying to give her direction. Put a bit more bend at your elbow, and pretend they're glued to your hips - this should help to keep your hands from moving forward and becoming uneven. Also, when you do have to use your reins for an aid, a take-give motion is more effective than a constant pulling back.
As far as your position goes, you need to sink more weight into your heels. It also looks as though you may just be standing in the stirrups instead of rising naturally with your horse. It might help to drop your stirrups & try posting without the help of something under your feet. This will force you to rely on muscle strength to post up, instead of relying on your stirrups.