Like jay was in a state of shock when he saw Ben kill heather and then had Phil pressure him into keeping quiet - didn't stop Shirley blaming him did it?
Shirley wasn't still in shock 2 weeks after the event when she was measured enough to demand money from phil to stop her going to the Police was she? She could still have gone to the Police then, they'd have believed her then, be able to do something about it but she choose not to. That decision makes her 'hatred' of phil ring very hollow to me. If you are really disgusted by someone, hate them and they are gulity of a serious criminal offence, especially one involving your best friend, you tell the police and take revenge (not to mention moral justice) that way. Her not doing so let him off the hook as far as I'm concerned.
What does Shirley say to denny or sharon to make him kick her chair. He's been in nearly a year and never behaved like that, I'm thinking he is probably provoked in some way. Even if not, you don't turn on a child, someone else's child and hurl the abuse that is in the dialogue extracts at them, even if they did kick your chair. She's a bully, picking on those weaker thaan herself, jay, ian, Denny and in that sense she and phil are well matched.