There isn't any glaring evidence.
I used the forensic package you linked to on one of my Photoshopped photographs and it didn't tell me much. Only thing it showed was a bit of cloning where I had done some, but also showed some where I hadn't. Opened the photo in question with it and couldn't see anything of note.
Zoom in on the Maxwell on her own photograph and look at the material of her top. You'll see a repeat pattern indicative of cloning in Photoshop. Her arm is blurry. Looks like cloning used to cover up the removal of the other two from the image with all three in. There are more things in the image of Maxwell on her own which look faked to me than in the one with all three in it. Talking as someone who uses Photoshop - not as a qualified forensic analyst of photographs.
Thanks for that, yes I agree the ones of Maxwell and Guiffre on their own are heavily shopped, for whatever reason. Have you watched the video I linked to? Here are some of the more convincing things he pointed out:
The shadows to the right of the door frame and Virginia and the shadow from Andrew's belly look fake.
The natural shadow made by the sphere on the banister looks unaltered.
Andrew's left elbow would have been lower in reality than the slither of left forearm shown would place it.
The angles of the barristrade on either side of the doorway are different, suggesting the photo was taken from the side. This suggests the flash ought to be oval rather than circular, hence the window is a separate photo.
The lack of detail in the central lower part of the photo- apart from Virginia's leggings its very dark, whereas the outer lower parts are very bright.
And other features such as blurring which could have been done to obscure editing.
But there is other evidence that Virginia would need to explain, such as why she is taller relative to Andrew than in real life. Why she was dressed for summer and the window open when the temperature was in single figures.
Why she wasn't wearing a dress that apparently she had gone out to buy the same day in order to wear for the prince.
Why the bathroom was, in reality, not as she described it.
My impression of Andrew that he is telling the truth. I get the opposite impression of her.
Sorry for the long-winded post but I felt a summary would help.
The analysis website was used only to see if the window frame could be detected beneath the shadows, IIRC. Otherwise it doesn't help that much, I agree.