You should have added a touch of blue on her face and darkened her face. Maybe added some grain or... blur or something to make her less HD-y vs. Kirk.
Hm... You gotta tweak around a bit to get it super perfect. That's what I did with Morrissey.
Thanks for the tips. The original shot had the focus on Kirk, with Saavik a little blurry. So I went with keeping that focal perspective. I did add blur, but you're right that there's still more information there. The lighting is too warm, so a little blue would probably help. I wanted to try incorporating some of the reflections that were on Saavik's onto Sandra's, but that'll take much more work.
The trick is to start with a photo of the "add on" person having the same lighting angles. Looks like you had that with Morrissey to start and then accentuated a little.