Hello:
I, too, have trouble with the choreography. I hadn't done any kind of aerobics for around 10 years. I've been doing my cardio on machines at the gym. (I still do cardio at the gym on the machines but I also do Cathe at home because it is so much FUN!)
I agree with starting with her older workouts and go through them in the order that they are made. I started with her Basic step workout for beginners and then, went to her Low Impact one that said it is for beginners/intermediate.
Here is something else that helped me. I got the Low Max workout (which I love) and the IMAX 2 DVD (which I'm in the process of learning now.) My main problem isn't the cardio aspect of the DVD's, it is learning the moves. When I first started learning Low Max, I found it frustrating because I would have a problem with some move or another. (I had some kind of mental thing with the reverse up Mamba down move and it took me forever to get it.) Ii would have to rewind and do the move over and over again. I found it frustrating because my heart rate would go down as I watched and tried the move. It felt like my workout was being interrupted. So with the IMAX 2 what I've been doing is to do a workout I know how to do like Cardio and Weights or the Low Max one. Then, when I'm done with that I feel like I've done my workout, because I have. I will then, do one or two chapters of the Imax 2. I don't worry about learning the blasts because while they are challenging to your heart, the choreography is easy. I don't try to make a workout of the chapter(S) I'm trying to learn, I just try to learn the steps. If I have to rewind and watch it twice and try it four times before I get it, no big deal since I'm not trying to 'workout', I'm trying to learn. I'm up to chapter 6 of Imax 2 and so far it has been working great. Next I will do a premix of segments 1-5. Imax 2 has short cardio and blast segments compared to Low Max and Cardio and weights, so maybe it is easier to learn, I don't know. However, when I first watched it all the way through I didn't think I would ever get it.
Keep trying, you'll get it. If I can do it, anyone can.