OP, why not just sign up for a lesson and see how it goes? Its not a marriage contract - if you like the lesson, you have your answer.
When I taught, it couldn't matter less to me how the student viewed themselves; what mattered was how I judged their skill level on a horse and what I had to offer them. After all, isn't this why you are paying someone? To help you further your skills and add new tools to your toolbox?
I've had students claim many things, both positive and negative, that weren't accurate. Let the trainer do what she's best at - what you're paying her for.
And honestly, if I received that email, I would label you as someone I wouldn't want to work with. As others have said, my time is precious and I want to work with people who are looking to learn everything they can from me. Your email makes you sound like you need coddling, and while I pride myself on being a positive teacher, I can't stand whiners, and the email sounds like you could potentially be high-maintenance, and not worth the aggro.
QUOTE: "My favourite people to take lessons with are the ones that are able to laugh at their mistakes, but still be slightly perfectionists about their riding." Save this for your diary. Don't imply that a potential instructor is or isn't any of these things. The potential trainer couldnt care less at this point whether they fit into your preferred mold.
Just go and take a lesson and try the trainer on for size. The rest is hubris and will do exactly the opposite of what you intended.