She looked very good during the actual jump part of the video. It's the approach that worries me. The rushing that was already mentioned.
I clicked on your other YouTube movies and saw the one of you cantering Dixie as well. In the canter video, she seemed somewhat relaxed, just going along with steady rhythm, BUT the whole time she is just braced against that standing martingale! Her head is raised as high as allowed and her back is very stiff. You seem to be holding her on a very tight rein for a greenie also. Is it possible to get her to work long and low? Or does she just run off if allowed on a looser rein?
What type of bit is she being worked in? Do you not have the authority to remove the martingale either?
As for you, I like your nice solid lower leg on the flat. Over the jump, your back looks great and just a little more release would be nice. Your helmet seems to have fallen off sometime before the cameraman started filming...