You need to get her front end moving and her back end moving each on their own... do you know how to do that?
If not, here you go: to get her hind end moving I want you to open your inside rein a bit and with your thumb up pull back towards your him and use your inside leg to push her hind end around. Once she crosses over let her walk out of it. Do the same going both ways. Make sure that when she does it you let her walk out of it so that she knows that is what you want. For the front end it is a little different you want to walk forward using that outside leg (not to far back though) to push her over and inside rein. Once you get each part moving then they can work together
Hope this makes sense.