This problem is not new. I have seen many people do that with their children or children of close relatives.
Your aunt probably dressed you up like a girl because she must have wanted you to be a girl. Some people both men and women have a liking towards a certain gender of children. Some are in love with girls and some want baby boys. So there are many people like your aunt, who have a deep desire to have a certain gender of children. Your aunt probably wanted a niece instead of a nephew. This desire was so strong that she saw you as a girl and dressed you up like a girl as well.