Using empty background to remove background of a scene with person

Hi friends!

My daughter asked me to shoot her a video in wich she appears dancing with herself as if she had a twin sister. The background is not a flat color, but the living room.
I have this footage:
1) video of my daughter dancing in first plane.
2) video of an empty background.
3) video of my daughter dancing in second plane.
I was convinced it would be a combination of blending modes with some Keyer or Luma, but I haven't achieved the effect.
Can you point me to the right way of working this, please?
I attached some stills as reference to show what I mean.

Thank you in advance.

Juan

Technically this is called a Clean Plate composite, and I don't know anyone who does a Clean Plate plugin for FPCX. Phyx used to have a great one for FCP 7.

Anyway, you can't really "key" out that sort of background. Keyers work on a solid color background.

What you want to do are animated masks. Something like Coremelts's SliceX that can track masks could help.

Don't let the dancing twins cross in front of each other, or you'll have a nightmare on your hands. Without very complex, very time-consuming compositing work, it won't work...

Have a look here: