The ornamental design for a milkfrother, as shown and described.
FIG. 1 is a perspective view of a milk frother incorporating the design of the present invention, showing the top, front, and right side surfaces of the milk frother;
FIG. 2 is a top view of the milk frother of FIG. 1;
FIG. 3 is a bottom view of the milk frother of FIG. 1;
FIG. 4 is a front view of the milk frother of FIG. 1;
FIG. 5 is a rear view of the milk frother of FIG. 1;
FIG. 6 is a left side view of the milk frother of FIG. 1; and,
FIG. 7 is a right side view of the milk frother of FIG. 1.