I added a few little details to the wrists and ankles to try and help get the idea across that she's turning into the car and not just strapped to the axles.
OMG this reminds me of an old tire commercial where they rolled people down the street and they gripped the tires with their hands and feet. I have no idea what aspect of the tire they were pushing but it always stuck with me for its sheer ludicrousness. Wish I could find it on Youtube.
I like the added detail to make the transformation clear and differentiate it from some sort of automotive bondage. Also, her look of determination is great!
I'm impressed with how you get the idea across so well without sacrificing either the cuteness or the strangeness of the character.
Superb job!