Photo editing to look thinner: Plus size model made to look slim; regular size

Photo editing request (example): "I am sending you a picture of my sister who is a successful plus-size model. She is now so secure in that space that she doesn't consider slimming down at all. I, on the other hand, think she has enormous scope to be very very successful as a regular model as well. She has the attitude; she has the class, and she looks real svelte. So to motivate her, I would like you to create a thin version of her photo."