They're not fake. Fake ones look balloon-like. Hers hang, even in a bra.
Maybe she fills them with water, like one makes water-balloons.
I cannot beilieve one would allow a condition, if real, such as this to exist; on the remote chance that they're real, it's a significant bodily deformity, a birth-defect, a handicap, a disabling characteristic, that can be corrected by surgery.