Yeah I get it now, thanks. I only remembered now that Holy wasnt totally succesful once it finally was summoned so it wasnt any loss for Sephiroth to take his time killing her. Getting revenge on Cloud makes alot of sense. Thanks for clearing that up. And now I know what Hubris means. Hurray.
And here I am, chiming in with the obligatory note that it was not in fact Sephiroth who killed Aeris at all, since he was currently encased in materia in the Northern Crater. Most likely, it was the shapeshifter Jenova, who chose to assume the form she knew would most strongly resonate with Cloud, although there are indeed alternate theories about who, exactly, it is that is responsible for Aeris' death.
Im pretty sure it was Sephiroth in control even do I agree with the belief that his real body was in the northern crater. Personally I think it was Sephiroth who killed her with Jenovas power.