Answer:
They WERE but in the end they are not. It actually shows that Raven intentionally let Terra stay stone... because, in things change, she says that she tried everything she could and none of her spells worked. However, the reason Terra was freed, was because in the END part 3, Raven cast a spell that turned all the people who'd turned to stone back to human, freeing Terra. She didn't even think about the fact that Terra would walk the Earth again.