The ornamental design for a chandelier light fixture cup, as shown and described.
FIG. 1 is a front view of a chandelier light fixture cup shown attached to a chandelier with all elements of the chandelier, including other light fixture cups, but for the one chandelier light fixture cup, shown in phantom;
FIG. 2 is a front view of the chandelier light fixture cup, the rear view being a mirror image of the front view;
FIG. 3 is a top view of the chandelier light fixture cup; and,
FIG. 4 is a bottom view of the chandelier light fixture cup.
The phantom line environmental showing is for illustrative purposes only and forms no part of the claimed design.