Maybe the author did not use an actual picture of herself and the "supermodel". Maybe the picture is just a random one found online....
IMO, I think it's a picture of the author. However, I think the SIL might be two different people. It might be the hairstyle and make up, but looking at the pics it looks like it may be two diff women. I dunno. I wish she would just reveal who it. This really blew up in her face. We're all wondering who the SIL.