I agree about not wanting her first visit with the farrier to be a crash-course. However, if her hooves are as long as you're implying, it needs to be done ASAP.
Once they get overgrown or worn down awkwardly, after a while the bones in the hooves, coronet, and pastern will start turning and if left untreated can lead to permanent lameness--not fun!
I seriously doubt her hooves are that bad yet, as it usually takes many months to over a year for hooves to get to that point, and if they were you would notice right off, and so would the farrier.
You may have to sacrifice a little backtrack in training for the sake of her health--a tough decision, but one I've had to make in similar situations. Just make sure the farrier knows how to handle a difficult horse; a good farrier can handle just about any type of misbehavior with just training tools, so look for someone that won't use drugs--that's a sign of someone who can't--or won't
--handle a difficult horse (I've had lots of experience with them...
If her feet are hurting her from being overgrown anyway, then working with them might not make a difference because having them handled will be uncomfortable.
In the end, I would say just get him out as soon as possible even if you don't have time to work with her hooves, then wait a week afterward. It may take multiple trimmings before her feet feel right; the farrier can't take off all the extra at once when the hooves are really long because the veins need time to recede. When they are in good condition, then work on having them worked with.
I would not suggest this while her hooves are being rehabilitated, but if access to a farrier is uncertain, then while he/she is over for the first few visits, ask them to show you how to trim and what to look for, and get your own pair of quality trimmers. This way if you get in a tight spot between farrier visits, you aren't at a total loss.
Hoof trimming is a very good skill to have, even if you withhold it for emergencies. Of course though, a qualified farrier should be used whenever possible.
I can't tell you how many times I've had to even out hooves between farrier visits when they chip or wear down awkwardly!
Sorry for the ridiculously long post, but at least I didn't go into teaching her to have her feet handled--that's at least another one of these posts worth!
I hope I could help!