No, dont do canter half pass if you don't have it easy in the trot.
What other stuff are you incorporating into your warm-up?
My mare used to be like this. I'd think canter and she'd canter in place. Or I'd go to use my outside leg around a turn, and she'd canter. Any small aid turned into a huge one. She is like a magnifying glass to my mood, like you said about yours.
Any time she was too touchy, I did something extremely simple for that day. Like walk, trot, walk trot. Then I'd put her away. If the next day was better, I'd ask for more stuff. But I would never ask her to do difficult movements unless her brain was in the right place.
You need to get really really boring. Don't try and fix every little detail, just set a goal for that day, and tune out all the other stuff.
Mares like this are tricky because their want and need to please causes them to worry. When they don't feel like they're doing the right thing, it upsets them. So you need to help her out and ride her a bit more sympathetic and do something really easy so that both of you don't even get to the point of being upset and frustrated.
Now, I can do anything with my mare because she is relaxed. So get her relaxed first, then work on all the harder exercises. :)
In riding, a horse's energy is like a river- guided by the banks but not stopped by them.