Ok, you're getting this reaction from her because she's NOT collected, or even engaged/on the bit. Dropping her head is not collected.
You need to engage her hind legs, which will them allow her to push off the outside hind into the canter transition, without losing her balance.
Right now, it sounds like she is unbalanced, so runs into the canter transition, and when she finally breaks into it, she's still unbalanced so has to canter super fast to stay on her feet.
You need to slow everything down, and concentrate on her hind end, not her head. Don't even worry about her head being stuck up in the air, all you want right now, is for her to place more weight on her hind legs, than her front legs. The head position will develop as she gets stronger.
A really good exercise that I love to use to improve trot-canter-trot transitions, is to start on a 20m circle in a good, active trot. Leg yield off your outside leg, to make the circle around 15m, then start to leg yield off your inside leg, towards 20m again. At around 18m, ask for canter, while continuing to leg yield off your inside leg. Canter only half, to one, 20m circle, then come back to trot and immediately start leg yielding off the outside leg again.
This exercise has helped immensely in all of the horse's I have tried it on, that have issues with balance and engagement in the upwards transitions. Basically you are connecting the inside hind to outside rein, which will begin to develop a swinging back and gradually the transition will become more balanced, softer and more engaged.