The key thing is the fiber content. Don’t confuse type of fabric , i.e. chiffon with fiber content. Fiber is wool, cotton, silk (all natural fibers), polyester, nylon, acetate (all synthetic fibers) If a pleated skirt has 50% or more of synthietic fiber it can take what is called a “permanent pleat ”. The reason the pleat is permanent is because the fabric has been pressed at a very high heat which actually melts the fibers. When they cool they will not go back to their original flat form becasue they are permanently creased into pleats. But a silk or wool skirt cannot retain the pleats if washed. They need to be steamed back into shape at the dry cleaners (or by you, but this might not be too easy if you are not very talented with an iron, lol)
So check the label and see what the fiber content is. If you want to play it safe, just go with the dry cleaning.