Any helpful tips on how to get stubborn horse moving on lunge?

I bought myself a young mare to break in. She has been a pleasure to train. Just one problem is that she is too quiet when it comes to lunging. She understands the concept and walks on when I tell her to but won't go to a trot or canter. I have cracked the whip behind her to make a noise and she just ignores it and it even use the end of it to lay across her rump - I don't hit her with it, just touch her in the hope that she'll move away from it - and it does nothing. I have got her trotting under saddle no problem at all, just can't get her moving on the ground. Any help would be appreciated :)