Glad to clarify that!! I was just imagining this pony that was all made of neck with no bum or back muscles.. hehe!
As for the pulling the head down, the likeliness is lack of muscle development, but it is a native pony, and not wishing to be rude about them, they are sneaky little things at times, and I have ridden rein-snatchers when I was younger, who used it as a method of removing the riders contact and therefore removing control, and having a giggle about it! Looking back now, I realise that with better riding this would not happen, but as a little 10 year old on a very strong native, you haven't really got much strength of seat. So, a possibility is that if your position is a little bit weak, and you are being pulled out of the saddle as she does this, it may be her way of saying that your contact is too strong or jerky.. perhaps moving up into the upper pace you are inadvertantly jerking on the bit a little, so she is trying to loosen your reins before she moves up a gear. If this were the case, you would need to work on acheiving an elastic contact.. one that is always there and always has a contact with the bit, but one that gives softly through the shoulder and arm. Note that the hand should not really allow the rein to travel through it, else the contact will loosen entirely rather than just softening.
Another possibility is that she is in pain from a badly fitting saddle, uncomfortable bit.. and of course she could just be being cheeky, but best to rule out everything else first.
The most probably reason is lack of back muscle, which should build up with more correct work
Rachel xx
