10/04/2011 at 02:00 PM EDT
When Amanda Knox's murder conviction was overturned
by an Italian jury on Monday, she was free to do something she hadn't done in four years: touch the grass.
During her four years
in an Italian prison, Knox, 24 – who was studying abroad in Perugia when she was accused of the brutal 2007 murder of her roommate Meredith Kercher – spent 22 hours a day inside an 18-ft.-by-13-ft. cell she shared with at least one and sometimes as many as three other inmates.
Every morning, "Amanda would wake up early, make herself coffee, then go out for one of her two hours of outdoor time," her mother Edda Mellas tells PEOPLE in this week's cover story.
The onetime linguistics major and avid athlete (she was a keen rock climber before her incarceration) tried to stay fit by walking in the concrete courtyard and doing sit-ups and push-ups in her cell. Still, she lost so much weight during her imprisonment that she dropped from a size 6 to a 0.
Says her mom: "We won't know the extent to which Amanda has changed until she comes home ... she has survived something horrible."
For much more on Amanda Knox's ordeal, including exclusive interviews with her family and a jailhouse letter she wrote them, pick up this week's issue of PEOPLE