My lady went to the wakeboard camp and learned a great excercise from PJ marks.
start about 10 feet outside the wake heelside, lean back against the rope, and edge across both wakes without jumping, staying on edge the entire time. it is surprisingly difficult to do if you are used to flattening out at the wake.
When you can cross both wakes on edge without flattening out, increase your angle of approach a little bit each time, and add a push at the wake.
It is going to feel like you are going incredibly slow, and you might not think you have enough speed to clear the wake, but if you continue on that edge, you will accelerate all the way through the top of the wake.