The problem is that no matter what I do to try and send her away (flailing my arms at her, running towards her while yelling, cracking the lunge whip right behind her etc...) she just looks at me and doesn't run away.
I've had a couple of experiences with overly desensitised horses & I wonder if she's been a beginner Parelli-ite horse or such, that they overdid & never progressed past the first game. Is she a new horse for you?
I don't personally think much of 'join up' but whether or not you want to do it, I think it's important to think about what you want to achieve from it, and she needs to learn to respond to you first.
I have literally had her walk backwards around the entire full sized arena. The thing is she looks kind of scared ... If I manage to piss her off enough (typically after 20 minutes of this) she might start turning her butt towards me which makes me uncomfortable. Like, I don't want her to kick me. I WILL NOT hit her to get her to run away from me so don't suggest that.
What are you perceiving is the point of doing this?? I just don't get why you'd continue to want to do something to scare her & 'piss her off'? And yet while you're apparently happy to keep doing that, you refuse to consider using effective pressure. Am I missing something?
Also in case it matters she does not lunge.
That's a given, if she doesn't know how to respond to your signals. I'd find someone experienced to help you with her, so you can learn how to be effective. I'd personally suggest you re-evaluate your resolve not to use physical pressure, but if not, then I think the only way is to learn how to use clear positive reinforcement training. I think this is valuable anyway, and learning the *principles behind it*, whether someone is keen on 'treat training' or not, is invaluable to understand how to be an effective trainer. Look up 'clicker training' to learn more.