I would keep working on gaining control of her speed at the trot. When you ask her to canter, be sure you have good contact. If she goes too fast, slow her down. If she trots, cue for the canter again.
I believe that you had another post about this horse hating it when you tighten her girth? That, combined with her being bad at the canter, puts pain issues into my mind. If her saddle is not fitted just right, or her saddle pad is not the best one for her, or even the girth itself may be causing problems, or if she has an actual back issue, it could cause both of these problems. Have you had a good saddle fitter take a look at her? Also, if it is a pain issue, she should be obnoxious when other people saddle and ride her. If she is an angel for your trainer and bad for you, then you will have to work on respect issues.