That's one that's hard to offer good advice on without being there in person to see how your mom handles the horse.
It does, however, sound very similar to something my mom went through with Kody a few years ago.
It took both of us a while to figure him out (we were going from elderly Arabian geldings we'd had for upwards of 15-25 years each to a 4 year old mini stallion with an attitude) but after awhile he and I were coming to amicable agreement about standing still and not nipping. As soon as Mom took the lead though he became a holy terror, circling and fidgeting and pawing and refusing to stand. She's an excellent horsewoman but has some physical problems that make her less confident than she used to be and it didn't take her long to want to wash her hands of him. She was just so frustrated! She'd resort to shanking him and trying to back him up to get control and it made no impression on him at all. The longer she held him the worse it would get. And yet I could take the lead and he'd calm instantly and then stand like an angel without any correction at all.
My secret? I'd finally figured out that rather than being completely
insensitive to correction, Kody was actually
over-sensitive to people. The least little tension in your own gut and he'll mirror it and refuse to be calmed. It's like nails on a chalkboard to him! To prove it I did an experiment. I took him from her, did a brief deep breathing exercise and found that calm place inside of myself. Kody let out a deep breath, licked, chewed, and stood relaxed. Then without changing anything outwardly I thought about what it feels like when I'm running late and stressed and embarrassed and felt that tension erupt in my stomach. Before I could even open my eyes he threw up his head and started circling me the same way he had my mother. She was amazed and just shook her head when I was able to calm him again as easily as the first time. I proved my point.
It took another couple of years before she was able to change her behavior at a level that would make him happy and until then she had to step away during our prep time at shows so that both Kody and I could concentrate. What finally seems to have worked for the two of them is surgery. No, really!
When Kody had his stifle surgery last fall I was gone for most of the first two weeks of his recovery and it fell to Mom to do his twice-daily handwalking. (Thanks, Mom!) To her own surprise she found that getting out there and walking with him, spending time just being together and enjoying the grass by the roadside in peace and quiet did wonders. She stopped stressing, he stopped stressing, the bad behavior fell away and she was able to appreciate him for the first time. Once she appreciated him she was inclined to praise him, and his positive response only reinforced that relaxed environment. All it took was moving them both outside the stressful environment that was causing the problem in the first place and letting them simply be together with no expectations.
Now the
cause of your mom's problems with MacDuff may be very different but I'll bet the solution would work just as well. She isn't enjoying working with him anymore because everytime she gets him out it's stressful! The horse is stressed, she's stressed, nobody's happy.
Take a time out! Just go for a walk on a nice sunny day (or even a not-so-nice day!) and stop and smell the roses. Let the horse eat and stand there with a hand on his back just feeling him breath. Soak up the sun. The horse will relax and naturally start standing still as he's grazing, your mom will relax and can praise him for standing, and anything else she wants to do with him like obstacle work can be slowly and naturally phased back in on the trail in little bits. Pivot him at the end of the road to turn around and go home, walk through the mud puddles, stop and get the mail, sidepass him out of the way of traffic, that sort of thing. Keep it all very low-key! Trust me on this, it works.
Yes, he'll probably get nutty as soon as you take him to a show or other busy environment again. Lunge him hard for awhile to blow off steam, then hand him to your mom to go take another long walk and graze some more. Do this enough times and both she and he will learn to relax and work with each other instead of playing Who-Can-Irritate-The-Other-The-Most. From his perspective she's being crazy ("I'm YOUNG and the world is GREEN and I want to play and why is this madwoman making me stand here?!") and from hers he's the nutty one ("Why can't this maniac just STAND?! It's so easy!") As long as they're working against each other in an adversariel relationship they aren't going to get anywhere without a lot of frustration.
Step out of the box and address the root of the problem. It's amazing how much improvement can be made just by changing your outlook!
Leia
Edited to add: I wrote that aimed mostly at the problem of the way your mother is feeling. I'm sure other people will have excellent advice on dealing with the behavior itself (you said he's high-energy with you too) but I don't want it to seem like I think the solution any time a horse won't stand still is to let them graze! :new_shocked That's not what I mean. But I do think that some quality time spent merely enjoying each other's company without trying to DO something would help their relationship. Trust me, if Kody or another well-trained high-energy horse who knows better won't stand still my first reaction is to offer them an opportunity to work off a bit of that steam. NOW, if they please! *LOL* I'll give them another opportunity to stop when they're a bit more appreciative of it.
