My coming three year old mare was a hellion when I got her.....never had been so much as looked at by a human let alone haltered or led. To get her safely out of the barbed wire paddock she was in with her many paddock mates, we had to get a rope on her, rather than try to corral her onto the trailer, for fear of her running the barbed wire fence. Well we were a bit sneaky because we had to be, and she of course ended up thinking even further that humans are no good.
When I got her home, she was released into a small paddock with safe fencing with her sister, but with no halter, because there are trees etc that I was worried about and would rather her have no halter than get hung up on something just for ease of catching. Well, it took a while, but I built trust and got her haltered with a catch strap on it and left it over a weekend while we were home, and got her used to touch and leading, somewhat.
Well, this little filly just never got over her lack of trust/respect for the human kind, and I use those two words together because I do sometimes think that what we read as "sass" and "attitude" are fear responses, sometimes!! Depends greatly on the horse. In this horse though, I think it was fear. She was much the same age as your mini, fall of her yearling year.
I decided that round penning her would be a good way to go to establish trust and leadership, and only had this as a goal due to her age (another factor you may be dealing with, and rather than thinking she may not like to work, I would consider that she may just be too young to work, and needs to mature in body and mind before labeling her either way). I picked a cool afternoon and took her in and did basically what was described here already, I made her move out and only change speed or direction of travel by my command, both body language and voice aids, at a walk and trot only. I was waiting for the tell tale signs that a young horse will display when they are beginning to understand and give to your authority, which is licking at the mouth, head down, possible some blowing/clearing of the nose, trying to stop and turn into the center of the ring to face you. I agree that I don't always want a horse to face me in the round pen, but that is much later in training when they have learned what is expected of them in whoa/stand situation. At this point with such a youngster learning basic respect and rules, turning in to face the handler is a classic sign that they are ready to give and as the classic phrase goes "join up". Now, this filly was STUBBORN, and it took nearly 2 hours of slow and steady work to have her finally understanding that I was in charge, and showing all of these signs above. But, giving in to your self doubt, thirst, or boredom before the point where the horse talks to you and tells you he/she is listening and ready will only set you back as the lesson has not been learned.
So, once she was showing all the signs, I asked for a whoa, which she knew very little of the word, but by body language of stepping towards the shoulder, dropping your gaze, and ceasing all movement of your own, she did. I moved towards her and was able to touch her all over, sack her out with a towel, pick up her front feet, and generally be with her without all of her pent up fear. Yes, she was tired, but I wasn't galloping her for two hours, I allowed her breaks at a walk, but on MY terms only, and if she picked up speed without being told, I drove her forward even faster. We also did some changes of direction, which had a command of reverse, and were indeed a rollback on her haunches toward the fenceline, achieved by abruptly stepping in front of the line of her shoulder and dropping the lunge whip sharply to the ground in front of her as well. It should be noted that she was never once touched at all by the whip, it simply wasn't needed. So it's not about exhaustion, but being tired is OK, it's about her learning that humans are in charge, but nothing bad will happen either, and a beautiful release can happen.
This mare, who could have been read as disrespectful as she did swing her butt towards me at times prior to this, is now actually easier to train than her sister who didn't get this type of single, intense session in the round pen because she had been handled some and at the time didn't seem to need it. And, this filly does like to work, and eagerly goes out ground driving down the road and onto trails, pulls small logs, and is easy to be with. So, don't give up. It sounds to me like you're on the right track, and remember yearlings are babies!! Hope that all made sense.....just my story.
Katie