Hey
I'm into this the whole year along with other comp stuff, but in Fusion Studio so not in Resolve Studio. Just for you to know that my advice is influenced by my own workflow
...
Now, since your start is on the right tracks, why wouldn't you make the whole key in the Fusion tab instead of going back to the edit and try to make it with a track underneath ?
So if you feel like it, select your 2 stacked tracks and right click to Make a fusion clip. Go to the Fu tab;
Pull your key - the best* you can - on the S.Klaus girl and add a merge node : the sofa is now on the BG input of the merge node, SK on the green FG input...
This goes into one single media out node afterwards, now go check the result on the Edit page.
*There are so much to write here about green screen keys. Aside from lighting the green BG or taking a great attention to the edges or light wrap in the comp with the right dedicated nodes, too many people think it's a couple of click trick to make it, I've been experiencing that for years (fortunately, they're also consequently as much happy too when finding out more and more tricks to pull keys properly )So find how to use a CleanPlate node too (feeding the pink input of the delta keyer), and don't hesitate to add a saver node to export your scene from the fusion tab to check, to avoid the Resolve support of alpha in the Edit