Originally Posted by rubyrules
I just don't know if that's doing anything. Because tucking her head like that...she could be mainly using the muscles underneath and that's going to make it worse.
You do actually bring up an important point. If you have to force her head down and in by pulling on her mouth, you will be using the wrong muscles and only strengthening the bottomline. I don't know if this has been mentioned or not, but self carriage is imperative to avoiding this. Self carriage is where the horse holds itself in the frame that you direct it into. When the horse is lightly on the bit (soft, directing contact) and is holding her head and neck and back herself (as opposed to leaning, pulling or flat out resisting your directions), then, and only then, will she begin to gain muscle on her topline, but will also begin to lose a bit of that muscle mass on the bottomline.
Just be careful about asking her to hold a frame for too long at first. This is very demanding for a horse and can lead to fatigue if breaks aren't allowed. Good luck!