msscamp has some good ideas, and ArrowH makes a good point about starting out doing this stuff on the ground, i don't know if this horse is a real bucker, but you can't be too careful in my opinion.
this isn't an easy problem to cure, you've gotten some good suggestions already, but there's no ONE thing you can do to fix the problem, it will be a process. if you can't completely seperate the horses like msscamp suggested (no common fenceline) one thing you can try is you can tie this horse up someplace where she can't get away (like a tree) and force her to be seperated, this isn't the cure-all, but it's one step you can take - just make sure you know how to tie her and make sure you don't lose your nerve and try to go rescue/untie her if she starts thrashing around, you can get very hurt (so can the horse, just consider that while considering this advice). also, you can try to make the horse walk home and not let her trot, but something i'd say would be more effective is when you do get home, sometimes just tie her up and leave her for 10-15 minutes while you do whatever - the point being, she doesn't get it in her head that as soon as she's home she gets to stop working. maybe even tie her up awhile and then ride her off again, things like that can make a big difference. just try to make sure that you end the ride on a positive note where you called the shot - or at least make the horse think you called the shot, even if you have to cut things very short. i have the theory that the beginning of your next ride is a continuation from the end of your last ride.
we had a terribly buddy sour mare that we eventually cured, it took time. pm me if you'd like me to ramble about what we did, if not, there's lots of very informed horse people on here, i'm sure you'll get good advice