The silver lining is that you don’t have to use spurs! Good for you that you are unwilling to give up on her, and believe in her. I hope your faith will be rewarded.
I have pasos that are on the hot side and I don’t lunge before riding. I use lunging for training and exercise only. If I get them going by lunging before I get on, they want to fly for the rest of the day. Have you tried starting with a walking warm up when you first get on? Also, I use liniment and/or massage before I tack up -if my mount is a bit nervous, and really take my time grooming. If still high-headed, I use ground training techniques to get the focus on me, things like ‘sending’ or flexing that I can reward and start off with positive energy and understanding. The first thing my horses get is a treat for standing still as I mount and adjust positions in my saddle. They don’t move until I tell them to go. It sets the tone.
Buck Brannaman says that the best horse you’ve got will buck you in September. I take that to mean sometimes the cooler air and the pretty weather just brings out the need to sow oats, and I’ve got one that will give a buck if I try to rein him in sometimes on the cool days, I just laugh at him and he quits, it’s a rare thing so no need to make it bigger by letting him get a rise out of me, and all things considered I’d rather have a horse that wants to go, over one that has to be constantly urged, kicked or squeezed. You squeeze one of mine and you’re going somewhere PDQ.
Can you get a friend to ride transitions with you? This might help reinforce your requests for trot/walk walk/trot with your mare’s attention somewhat diverted by the other horse.
One other bit of advice comes from Alois Podhajsky: when your horse is high energy you have to be low low energy – keep the sum of both energies at 10. If she is a 9, you are a 1, if she calms down you increase your energy. When a horse has an undesirable behavior, the rider very often yields to human nature with a nervousness or a sense of dread, and unconsciously we raise our energy, have shorter breaths and tenser muscles. I sometimes do this on my gelding who hates dark pavement (he fell once) when we have to ride on it. I have to tell myself to calm down, and stop feeding his desire to panic – that’s how he fell the first time – although I was not the rider I was there and I saw him go down in a panic. Awful. I have to concentrate on relaxing and even-breathing, and the effect is remarkable.
How this relates is when you ask for speed, do you tense up expecting mischief? It may be contributing? If so it is a very human response. Just some thoughts from those much smarter than me. Hope it helps.
Alois Podhajsky: “When I hear somebody talk about a horse being stupid, I figure it’s a sure sign that animal has outfoxed them. ...