A friend of mine recently said "So, Dorothy is a zombie?" Well that depends on your definition. If it's as loose as "Returned from the dead," then yes. But when I think of zombies (and I think about them all of the time), I think of ravenous mindless hordes of decomposing undead.
Dorothy is not undead. When she returns from her grave, she continues to age again, grow, and all the things other little girls get to do. She has a second life.
She wakes up in a field, somewhere in Oz. Roughly between The Emerald City and the Land of the East. She immediately encounters some Munchkins who take her with them to the East, not wanting to leave a little girl out in the wilderness on her own. Along the way they meet the Scarecrow.