After reading the Celestine Chronicals, I definitely looked at Clash of the Titans (which I really enjoyed) in a new way. Perseus killing Medusa was messed up. It's even worse in the original myth though. He killed Medusa and took her head as a gift for his father in law...
In EG, I changed his motivation as well as the motivation of all the Olympians for killing their progenitors. I also "fixed" Medusa a bit. In one version of the myth, Medusa was mortal unlike her sisters. This made no sense to me. So in EG, Medusa is a primordial goddess just like her sisters, there is no "curse" from Athena, they were instead always gorgons by their heritage.