This pretty young lady doesn't need to lose any weight but sometimes you can impress others but discretely removing a few pounds. They'll be happy with the photo and not even know that you helped out.
Here's all you need to do.
Copy your image to a new layer.
Under Edit select Free TransformChange the width just a little to say 95% as I did in my example. (any more and it gets obvious and distorted)
When you're happy with the results click Return.
You may need to do a little cropping and then you're ready to save your finished results. Here are the results side by side below. The left is before and the right after.
It's simple, discrete and the best part, it's easy.