These are two types of fashion sense that people may want at present. Elegant slutty means that you will be able to wear clothes that are considered to be revealing, but you will wear them in such a way that you will not look like you are trying to tempt everyone that you meet.
Women who wear elegant slutty clothes may wear a low cut dress with a short hem but would be wearing accessories that will make the ensemble look more elegant than they should. Trashy slutty means that the person will just look trashy. The person would be showing all of her assets to the point that it may sometimes be too much.