So, it sounds like that is the key. If I decide to try and take her on I should be signed up with a professional trainer to get us to be a better skill match for one another. What should I be looking for in a trainer? I am assuming that the BO that trains children/teens to ride isn't going to be experienced enough to help us.
They don't have to be the highest priced or fanciest, just be able to prove to you that they're able to take two disparate individuals, and make them into a good partnership.
Most professional trainers don't do it 'on the side'; it's usually their livelihood. Whether or not your BO is capable of training you, I don't know. I would think if she's not doing anything except the basics, she won't be a good candidate to fine tune you and a horse.
The fact that you realize you're not capable of doing this yourself tells me you're already ahead of the game.
If Sophie really is the horse for you, then she'll come to you. If she's not, the right one is out there.
I wish you luck in whatever you decide. You certainly seem to have a good head on your shoulders.