As for what cue works . . . that is going to be trial and error :).
Cue: Tell her to feel her torso/pelvis move farther past the TO foot. It has to feel “different” than what she has been doing. Also, have her feel the thighs separate as the lead knee drives towards the hurdle. Her goal is to move down the track, so her torso/pelvis should continue to move forward through the hurdle with as little upward movement as possible.
There is a lot of good advice floating around and what works is going to have to be decided by you and your girl. She probably still needs more hurdle space in order to change the flight. With my current girl, we focused on the preceding two steps prior to each hurdle (She might need to slightly cut both steps in order to gain the space).
ALTHOUGH, we found that the entire rhythm of the race was set-up in the 4 preceding steps to the 1st hurdle. So we practiced to 1-2-3 a LOT, then practiced it some more.