Cute horse...I just recently sold my grey pony and i see small horses/ponies that look like her and i get really sad...
Your leg slid back over the second fence, but not the first, so it looks like its not an occasional thing for you. I would just say work without stirrups if you feel it becoming a habbit. I think that you could have more of a release, but it's not really necessary because you followed her head and never punished her in the mouth, and there was really no need for more rein.
you guys look like a cute pair!! Good luck in the future!