The most effective way will likely depend on what kind of a learner she is. Basically: visual, instructional/verbal, or hands-on.
If visual, I'd suggest letting her watch herself on video. Nothing high-tech, or even slow motion necessary. If it's horribly obvious to you, it will be obvious on film. If she's anything like I was, she has no concept what she looks like. Once she sees it, there is a chance she'll be able to adjust some things.
My H.S. coach told me numerous times/ways and it never sunk in. Then, one day I saw myself on video and it was like a light switch was flipped.
It might also help to show her a video of a "good" woman's stride too.
If she's a visual learner, she'll be able to make changes quickly.
I'd guess the drills would be best if she's hands-on. You might also have her try getting her stride count closer to 180. Running to a metronome is helpful. You have to shorten your stride to keep up with the 180 count.
There is a lot of truth to the earlier post about "just asking her". But, if you've tried that and she's not getting it, it might be the visual stuff above.