Lovely ! what a happy,relaxed horse

I have a suggestion for her if shes interested?
Try using a soft rounded leadrope,a smooth one not the twisted ones, then put a knot in the end and do the clip up round the inside of the knot.
That way she can leave it laying on the neck and only use it when she needs to which will train horsey to go only from the seat/leg aids . It will also prevent her tipping forward as she currently is to reach the rope in the trot. She has such a good seat she wouldnt be without that.
Also if she uses plenty of praise and reward he will be motivated to work just off the seat ( if thats what she wants, it may not be in which case ignore me

)