The Green Mile is strictly a work of fiction. The story and its elements were crafted to entertain and engage readers/viewers, not to represent actual happenings in the real world.
Yes, there was. In the 'Green Mile' novel, there are various characters, and a black woman may be among the minor or background characters, though not as central as some of the male characters.
It depends. If your local library has a large collection and high circulation, it might be easy to borrow. However, if it's a popular book and there are only a few copies, you may have to wait for it to become available.