Aww, she is such a cutie!! She will get the hang of it as time goes on.
She sounds just like my Scampers. He won't stack for the life of him. He hates it and he is very stobborn and will bunch up, it is so hard to get him in a nice pose. The only time you get to see him stacked beautifully is when he sees a squirrel or bird.
I am still working on it with him, hopefully in time he will get the hang of it.