Look away now if you don't want to know the book differences:
She gets a six month sentace for perjury - arrested in corridor outside court. She pleds guilty - serves three months and gets out on licence.
The file she created was deleted, she doesn't know if Guy read it before he deleted it (computer was seized).
The flat is Mark's wife's dead uncle's. We discover near the end that she whisperer to Mark in this flat (while he was semi asleep) that she wants him to kill George and smash his face in - earlier in the book we'd be told the same scene but slightly earlier (before he sleeps) he'd said 'you know what we're going to have to do' 'we're going to have to warn Craddock off', she asks how and he tells her to leave it with him.