Zombie Apocalypse

I write made up vampire books. Vampires that are from my own created world where they behave more human than the stereotypical dark menace. Yet to my older sister, this has, somehow, made me something of an expert on everything to do with the supernatural.
During my visit we sat up late discussing various way zombies might take over the world. How would they go about it? Would it be the final awakening of the dead and they would come back to destroy of for ruining the earth? My sister's eyes grew wide at the thought. Would zombie simply be the term used for some flesh eating disease that might annihilate us? She could see that happening too.
I hated to bust the bubble of the gruesome conversation but I believe we'll be hit by another meteorite and everything living will be wiped out in an instant. Except, of course, for roaches and alligators.
Hopefully, life will slowly swirl the primordial ooze until one cell organisms split again and crawl onto dry land.
Hopefully, they will be a little more advanced than we...take a little more care with the environment.
My sister didn't care for that scenario at all...