How to make ONE object disappear in a video

I know how to make all moving objects disappear at once by layering two versions of a video on top of each other (one without the moving objects and one with the moving objects) but I was wondering how to only make ONE of the moving objects disappear.

I have not filmed any footage yet. The storyline is that there is a mother and a daughter sitting down at a bus stop. As the daughter reaches her hand over to touch her mother's hand, her mother slowly disappears. How do I film and edit this?

Thanks in advance.