Im not sure if you mean lening on the reins or just plain pulling her head down to eat lol
Is she collected up? Or on a loose rein? Is she sore in her back/neck/legs at all? It all depends on these things a little, but if she is leaning on the reins, loosen you hands a little, as she would be pulling back to your pressure, this is her way of telling you "hey, im doing what you want, so why am I getting pulled back?". And also use your legs to make her a little more energetic! And if she is pullin her head down to eat, say a firm "NO" and kick her on.