She used the fingers to make the butt more round, then pushed back the butt and put the upper body to the front. You can clearly see her butt is closer to the camera than the middle of her back. Then you take a picture very close to her butt and slightly below it. So the angle make her waist look a lot smaller. Maybe she used photoshop, but this can be achieved without it for some women. Most women can't but we don't post most women here.

r/InstagramReality is mostly bullshit, circlejerk for people who hate those models just because they make a lot of money. A lot of posts the fake one is the one they say is "real". In many others is just a question of angle, posture, lightning and make up. These can make wonders, that's why some photographers and make up stylists are very well paid. And that was true long before photoshop was created.

Some women really photoshop their images to alter proportions but a lot of them don't. They just are exceptions, women with a body unlike most and they know how to exploit that in pictures. Some people hate them because they make money just posting sexy pictures, like it's their fault. Some have good academic credentials, among the women posted here I saw physicians, nurses, lawyers and engineers. But many make a lot more money posting sexy pictures. If people paid you a lot of money for selfies wouldn't you do it?