The ornamental design for a booth for washing pet animals, as shown and described.
FIG. 1 is a front perspective view generally from the left end of the booth for washing pet animals according to the principles of the present invention;
FIG. 2 is a front perspective view generally from the right end of the booth for washing pet animals of the present invention;
FIG. 3 is an elevational view of the left side of the booth for washing pet animals; and,
FIG. 4 is an elevational view of the right side of the booth for washing pet animals of the invention.