Can't be. Midnighter has her left thumb hooked in the material of the boobwindow, and there's no line of with/sans gauzy material to indicate that there's gauze on only part of it. It's possible that there are a series of thin strings holding the boob window partly closed which also hold the gold chunk in place, though.
Also, her boobs aren't swarthy; they're somewhat-poorly-over-shaded in an attempt to make them look 3D. Easy mistake to make, since you were looking for a believable explanation for the stick-on boob-dot and that'd work, but given that the coloring is inconsistent across the full area of the opening...
I'm gonna go with the almost-invisibly-thin network of filaments with the mega-dot as the nexus in the middle.
...Can't believe I'm suggesting this, but they should've just gone with either a one-piece-swimsuit-style leotard or a battle bikini with a halter top and boyshorts or something. The one time it would have made perfect sense, since Apollo is solar-powered and borderline-invulnerable, and they waste it.