You will notice during playback that the dress (especially the straps) do not actually touch the body. This is because the collision volumes of both the character and the dress are too thick. This means that Maya believes the two are in contact when they are not. You can fix this by adjusting the collision thickness of both objects.
To adjust the collision thickness of the dress
Notice that the simulation appears exactly the same as before. This is because you are actually playing your cached simulation. In order to view your changes, you will need to make a new cache.
To make a new cache for your nCloth simulation
Maya automatically plays back the nCloth simulation and saves it to disk as a cache.
The dress now appears to rest on the character’s skin.