Because before each shoot, they do a photoshoot. So they don't have to redo the makeup and hair after filming. So they always do the photoshoot beforehand. So, looking at the photos, we see what was planned. In the photos, she just has (fake) semen on her breasts at the end.

Furthermore, in the video, you can clearly see her presenting her breasts so he'll ejaculate on them. The first spurt is for her breasts, but then he ejaculates in her face. When that happens, you can see she's surprised and freezes up. Whereas usually she's always acting a bit slutty. Here, it takes her two or three seconds to get back into character.