This is basic leading skills, a trainer would help, but if she's set on doing it herself (and I don't blame her - I'm so that type too!) here are some ideas...
Bring the horse into an arena or fenced in dry lot so you don't have to battle the grass until the basic respect is first earned.
I would start with backing up, as this will help correct much more. I would start standing in front but a little to the leading side of the horse (so if he decides to jump he doesn't hit her) - I'd take a firm step into his space and apply pressure on the lead rope pushing back (so the pressure is going mostly on the top of the nose band of the halter) until the horse leaned back I'd immediately release the pressure and rub out his nose (if he appreciates that, if he doesn't like it just leave him be). I'd repeat this until I got several steps back for one assertive step in his direction and the verbal "back up". Make sure the timing of the release of pressure is immediate when he tries to do the right thing and make sure the pressure stays on or gets firmer if he does the wrong thing (like turning away or walking forward). Once he's solid on backing up from nose pressure I'd practice it a little from standing beside him like while leading, it shouldn't be hard for him to connect those dots.
From here I'd work on the basics of leading. I'd walk a few steps with a "walk on" cue and stop while saying "Whoa" if he kept going and didn't stop with me I'd back him up to where he should be. I'd repeat until he figured out it's way easier to just stop with you than have to back up a million times.
Then I'd work on teaching him to yield his hind end (disengaging his hind quarters) this can help "unstick" a horse who's ignoring you. I'd hold his rope so he couldn't move forward, but stand at his hip, I'd apply pressure with my finger tips to his hip area (the firm muscle part, not the bone). The moment he leaned away I'd release the pressure. I'd repeat this until he was turning his hind end progressively away, crossing hind leg over hind leg, with front end just turning not walking anywhere.
I'd do this same thing with his front end, making his front feet circle his hind feet.
I'd do the same thing on his middle, making his side step both front and back.
Now you have control of every inch of the horse
I'd go back to walking, this time I'll add turns, mostly turns toward the horse, making him yield away from you, but also some toward you where he has to maintain his distance at all times.
Then I'd add the obstacle of grass you can use yielding or backing or even just a good schwack with the end of the rope to get him to get his head up. Then firmly marching forward to wherever I was looking.
She can use these skills to teach her horse pretty much anything from here on out.
At least those were all the things I did do to teach my horses to lead before I found clicker training and all I needed to do was hold out the target and my horses would keep their noses glued to it, no matter what obstacle was in the way, jumps, water, tarps anything! I found that a much more fun and rewarding way to train my horse to lead where I wanted and found they carried on the skills when the target was gone and it was just me with no tack :) They follow me through anything now and I find it works exceptionally well for those laid back horses who could use a little more enthusiasm :P but I don't think that's how 4H works yet so your friend should probably stick to the old-school methods.
But if she (or you) are curious here's some info on CT - Clicker Training: Challenge Accepted