First, if she is already a beginner, and only riding beginner trails, it may be hard to get her to do this since there is no "easier" trail to have her attempt it on.
I usually have people strap in on the flats, and say "put 50% of your weight on each foot... okay now put 75% on the back and 25% on the front... now put 75% on the front and 25% on the back." Then I take them on to the hill and I'll unstrap, have them point their board downhill and hold their board still. I go through the same process, because it feels way different to shift the weight forward on a hill. When you think you are 50/50, you are actually in the backseat. What FEELS like 75% on the front foot, is actually 50/50. This feeling is increased on the steeps. Even today, when I'm riding the steeps, I have to keep telling myself that even though I feel centered, I'm probably in the backseat. Once I shift I can usually hold an edge better.
As for your first question, yes, you have the right idea, however if you are carving at high speeds, especially on steeper trails, you will notice that if you have too much weight on your front foot, your tail will wash out a bit and your carve will turn into a skid. It is important to change your weight balance a bit as you go through the turn. So to initiate the turn, you have more weight on the front foot w/ your knees bent, as you get through the halfway point of the turn (the apex) you want to be more centered w/ your knees extended, and as you exit the turn, you want to have a little more weight on the back foot (knees bent again) to really dig that edge in. This keeps you carving while traversing instead of skidding. I'm not talking about being all the way in the back seat, but a little more weight in the back foot will help. If you keep all your weight forward, you will notice that as you complete your turns, you will skid a little bit as said previously.