This is very close to being an inversion as performed. It might be an inversion. It’s close enough that I wouldn’t have a problem with an official calling it an inversion. Before moving on, if the top person looked up, it would likely lift her shoulders and lower her hips enough that it would not be an inversion, and would be legal regardless. Also, if they lowered her foot slightly, it would lower her hip so that it wasn’t above the shoulders.
Let’s assume it’s an inversion. By rule 3.3.6 (b), someone needs to be on the upper body of the top person. As I see it, no one is in contact with the upper body. Her hands are on their shoulders, but that’s different than them being in contact with her, in a position to protect.
However, there are two very easy ways to fulfill this requirement. 1) Have one of the bases take their front hand out from under the foot and grab her wrist or put it under her shoulder. The secondary base is the ideal one to do this. 2) The other option is for the back spot to grab the top person’s wrist with one of her hands. With either of these options, someone is on the upper body and could help protect her by pulling up on the arm or by pushing against the shoulder.
Once they dip, the hips go down and it’s no longer an inversion. At that point, the person on the upper body can release and move to whatever position they needed to.