Her family origins are confusing, as they tend to be. Some claim that her parents were Zeus and Nyx, Goddess of Magic; some sources state that her only parent was Nyx. Other sources name Oceana, the world ocean, as her mother. She is also named as sister to the Moirae (the Fates) and the Keres (the Black Fates).
If Zeus were actually her father, then incest would enter the picture. Zeus was very attracted to her and brutally violated her. She ran and he would always chase her. She once transformed herself into a goose, her sacred animal; Zeus followed her and transformed himself into a swan, once again forcing himself upon her. Nemesis laid an egg, which was found by a local hunter. He gave this egg to Leda/Lede, who raised the child as her own. This child turned out to be the legendary beauty, Helene of Troy. This story takes a different turn in another version of the legend, in which Zeus, as a swan, actually rapes Leda. Mythology can be confusing at times.
While She is the Goddess of Divine Retribution for evil deeds, arrogance in front of the gods, or undeserved good fortune, Her name is roughly translated as “giving what is due”. She gave out punishment and unhappiness, but she also granted happiness and good fortune; She maintained the balance of justice.
It was Nemesis, angry at the way Narcissus treated his admirers and the mortal women he pursued, who lured him to a still pond. When he looked into the pond, he fell in love with his own reflection in the mirror-like surface. He was unable to pull himself away and, thus, withered away and died.
She is portrayed with wings, riding a griffin-drawn chariot. She has been depicted with a sword and scales, but more often than not, she was seen with a whip, a rod, a dagger, bridle or scourge (sounds like a most fun Goddess!).