How to calculate scale adjustment to match a background push or pull?

[spinachworld]

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

I have a subject that was shot 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 scale her down so that as the drone pulls up and away she appears to get proportionally smaller.  I've tried eyeballing it but it doesn't feel exactly real.

Is there an equation to calculate the amount I should reduce her scale, or where I should place keyframes over the duration of the shot, relative to the speed and height of the drone shot?

And since I'm not great at math, might there even be an easier hack for this?

Would this be better done in AE and if so how?

Thanks!

[Michael Grenadier]

definitely AE, but I'm not an expert so I can't tell you how to do it.  I think you track something in the image and then there's a way to "attach" something to the track.  Maybe if I have a few drinks, I'll remember.   doubtful, but possible.  Might try posting your question in the ae forum...

[Graeme Bull]

I would put a rectangle or some shape over top of a visible object near where the subject is going to be, hopefully about the size of the subject too. Then go to the end of the clip and scale that shape down to fit the object size and see how that scale looks applied to the green screen subject. Your point of reference will likely have to be eyeballed, practice, try, try again. Watch for focus too and desaturation etc. Those effects will help sell it I think if you don't have the scale perfect. Motion blur may assist too. All of this is easier to do in AE and can be a bit more granular as you probably have to motion track the position too.