I have an interview scheduled with the person the position reports to. I have already interviewed with HER supervisor, the divisional director. Went very well. No recruiter involved. Position does not exist - director wants to add a position. My email correspondence with the person I'd report to has been somewhat hostile (on her end), repeating the fact that there is currently no position available and that she's meeting with me because her boss insists. The position is a step down from my current position (I've relocated and can't work in my industry at the level I'm currently at), so she may be concerned that I'm after her job. I am not. I really want the job that the director wants to create.
I'd appreciate any advice about how to approach the interview and turn around her negativity about me. Thanks in advance!

Treat it like you would any other interview
Don't let this characterization change you. You should interview with enthusiasm and energy, having solid answers for the key questions, good questions for her about the position, and a solid close.
It could be a test. It could simply be her style (is she a high D and you a high S?).
You can't outgame this - so just do your best. That's your optimal strategy.
John Hack
I think it's the opposite -
I think it's the opposite - I'm a high D and SHE'S a high S!
It's not a test
I am amazed that an executive would say I don't want to interview you but my boss says I have to.
In email.
So therefore, I am guessing this person is not a seriously tenured professional manager. I could be wrong.
And it doesn't matter anyway.
Be kind. Be respectful. Show respect for her point of view that the position doesn't exist. (Hell, it DOESN'T - it's easy to agree with that). DO NOT mention her boss. Interview with her. If she gets into a discussion of why the position shouldn't be created, don't let her put words in your mouth. [There's a difference between agreeing with, "this position doesn't need to exist" and saying, "I can see your perspective, and I think there's value to be had..."]
So, expect some more direct questioning, put a little tighter rein on your willingness to engage in conflict, and prepare the way you always would for all the big questions.
You're a High D, and you have a connection to her boss she's not feeling. You're POTENTIALLY the classic example of someone who thinks that it's okay to mix it up, only to have her say to her boss, he's good, but he's a jerk.
The fog comes in on little cat's feet...
Thanks, Mark. That's great
Thanks, Mark. That's great advice.