Be cautious of lunging pre ride and depending on it to calm the horse down. Wear gloves and be in an enclosed area first time - lots of horses get wound and wound and wound and wound on the lunge until you have a dragon on a rope and it decides to take flight.
Also lunging is not the greatest thing on legs.
However I do think cantering in side reins adjusted correctly would help her to understand what you want in canter.
As far as for undersaddle - really focus on a good, adjustable trot.
When you canter my favorite "please don't bolt" exercise is to circle at a or c, ask for canter and then out of the second corner, yield steeply out of the corner across the diagonal until they trot, then praise and develop your trot again. It's not a remarkably pretty exercise, but it works!
Good luck :)
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