Ooh, that would make sense. I didn't think about Gemma but it seems like she has a similar delicate upper body and skin tone to the model in the photo. I also thought that it might be Vlada because her chest/collarbone area looks a bit similar?
I’ve had the same issue as you though where I can't find the original photo or the show that it came from, but I’ll look through some more pictures of Gem to see if I can find any info about it. Thanks for the help!