Years
It had been 3 years since Elphaba had defied gravity, defied all of Oz. And oh, what happened during that time!
Frex died about 2 years after she flew away; Nessarose governed in her sister's absence. She became bitter and oppressive, referred to as the Wicked Witch of the East.
Glinda was promptly trained in the art of being good: lying to the public, telling them only what they wished to hear. She became lonely, longing for Elphaba to return.
Elphaba was hiding somewhere; no one knows exactly where. Some say she went with the Animals; other say she went alone.
But no one knows for sure…even after her death, what happened to the Witch during those three years remains a mystery.