Are you using all of your aids to turn her? Like the rein, your seat and your leg?
My instructor always said turn your head in the direction, it causes your spine to shift which shifts your seat-bone weight and alerts the horse of a change before it takes place, then use your leg pressure with the rein. She may get it right off the bat, since you said she knows her stuff, or she may take a few tries. :) Eventually you can just start to shift your weight and gently touch the rein and she'll be cranking in the direction.