What could it have been? It wasn’t an earpiece because they can be really small. Could she have put her catheter bag back there?
She can't pee uphill, and what looks like the print of a wire (tube) goues up to her neckline, which, unless she is some sort of alien, is not wehre a catheter tube would go.
If what is showing (printing) under her clothing is some electrical thing, and i suspect it to be, the rectangular box is a battery and radio receiver, and the wire is both an antenna and wiring to an earpiece.