The long skirt is read as modesty, grace and a slower pace. Some dream books see in it a wish to keep something private, wrapped and flowing rather than on display.
Has this come up in your dreams before? What was going on in your life then?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.