The ornamental design for a ruffle edge cover, as shown and described.
FIG. 1 is top view of the ruffle edge cover shown laying in a flat configuration. The bottom view would appear the same as FIG. 1.
FIG. 2 is side view of the ruffle edge cover of FIG. 1; and,
FIG. 3 is an enlarged front elevational view of the ruffle edge cover shown in use covering a flower vase. The vase shown in broken line is for illustrative purposes only and forms no part of the claimed design.