You have to build up your trust in her. Just because you love her, doesn't mean you have 100% faith in her that she'll keep you safe when you canter. Start with walking, then doing a small trot, and then going up to cantering. Ask a horseback pro if you're still uncertain.
Is your fear for her or for you? I know that sounds odd but give it a little thought. I have cousins that train folks all over the world. Normally she deals with riders further along, but it starts at the beginning. Did you get tossed at some point or come close? Even if you haven't, now really for the first time your butt is in the air (I never worry about PC here-that's why my answers get axed) think about it-your bouncing where's the horn? Anyway, just take your time, be gentle but in charge at all times. If you need to yell do so, never let your horse know that you're afraid, talk with an instructor, let your legs do a little extra squeezing while airborne--you'll be just fine--excuse me I need to go make a baba (bottle)
I had an instructor that helped me when my horse had some chiro problems which we realized when he almost bucked me off at the canter. I was afraid for along time even though the horse wasn't in pain anymore I was still afraid. We knew that he wasn't going to do anything so my instructor said just do it and I did and am not afraid anymore. It typically only takes one thing to take away your confidence but once you do it again your fears typically go away. Start small if it really worries you. Then move up. Even if you do 3 or 4 strides of canter or trot really fast it still helps.