I don't believe Jenova is dead, it has a consciousness that surely must be alive. The relationship between Sephiroth and Jenova appears to be symbiotic.

What kind of throws me is that Jenova never sucessfully reunites. You've got Sephiroth with the head (and at least one arm) and the clones go to him rather than the main body of Jenova which is in Midgar. Somebody says at one point (I forget who) "Sephiroth wants to manipulate the clones himself" as an explanation for why they don't go to the Shinra building. I'm also not sure about the relationship between the Reunion and Summoning Meteor. And all you have for a 'Reunion' is (SPOILER) the 'failed' clone Cloud, Jenova's Head and Sephiroth . Some Reunion.