@AlbaNader1976 lookin at 21, they look like costume nips. So I'm guessin they're antigrav because they're covering her real breasts. Pushing them up and sticking them out farther in the process.
16 has a slight off tone to her stomach skin in a line.
So I'm thinking part costume, an part photoshop to remove costume lines. Just a third option to consider.
I think she'll have to moosh them breasts around for a while to get them to the point that they aren't fighting gravity so much.