Aurora:   I believe Aurora initially resisted Nemesis' bargain.  However, allies of the Outsiders discovered a 'mortal' child named Allison Ann Summers (born just before Grave Peril).  Bianca and others caused the thread between Faerie and Reality to thin, allowing a misled Agatha Hagglethorn to specifically make claim on the infant.  The infant turned out to be Aurora's.  You will recall that she has a remarkable amount of mortal/changling acquaintances (brought to light in Summer Knight).  Harry was able to save Allison Ann Summers in Grave Peril, but it was a close thing.  Nemesis used this to convince Aurora to accept the infection, and her ultimate goal was for Winter to hold dominion such that she would be able to walk off into the snowy sunset with her child.