The design consists of the visual features of the COSMETIC APPLICATOR shown in the drawings, whether those features are of shape, configuration, ornament or pattern or a combination of the same. The stippled line portions form no part of the claimed design.Figure 1 is a perspective view of the COSMETIC APPLICATOR;Figure 2 is a front elevational view of the design shown in Figure 1;Figure 3 is a back elevational view of the design shown in Figure 1;Figure 4 is a right side elevational view of the design shown in Figure 1;Figure 5 is a left side elevational view of the design shown in Figure 1;Figure 6 is a bottom view of the design shown in Figure 1; andFigure 7 is a top view of the design shown in Figure 1.