I'm with @drdance on this. This is anatomically and biomechanically impossible. Dancers and teachers use a lot of imagery, which can be extremely useful in the studio, but is often not anatomically plausible.
People have different propensities to increase muscle mass / cross sectional area. Yes, testosterone is one contributing factor, but also whether or not you are a 'responder' to strength training. Some people physiologically have very little ability to respond to strength training, and as such, do not easily develop muscle mass, and others develop muscle mass and strength more easily. There is nothing you can do to change your physiology. For most females however, even using the heaviest weights, will not increase muscle mass.
Unfortunately, Pilates will not change the shape of muscles. Everything drdance has written on this thread is scientifically robust and evidence based.
There are many vocational contemporary dance schools out there that will not discriminate against body shape, muscle fibre type or size. Those large muscles are wonderful, powerful muscles that can produce exciting and explosive dancing. Embrace them.
