How to adjust scale of a subject while background shot pulls or pushes?

[spinachworld]

In case that headline isn't clear, here's the situation:

I have a subject that was shot from above on green screen.  She's standing looking up at the sky.

I have a drone shot of a field that starts low to the ground and pulls to about 150 ft up.

I want to place her in the field and continuously adjust her scale so that as the drone pulls up and away she gets proportionally smaller.  I've tried eyeballing it in Premiere but it doesn't quite work.

How do I calculate the amount I should reduce her scale and where I should place keyframes over the duration of the shot, relative to the speed and height of the drone shot, so that this looks natural?

Thanks!

[Justin T - Hyper Brew · Accepted solution]

Do a 3D track in After Effects, create Camera and nulls, make her footage a 3D layer, and Shift + pick wip it to a null on the ground.

Here's a tutorial if you're new to 3D Tracking:
https://www.youtube.com/watch?v=PqFskLSlToY