I think Amber's friends probably feel guilty AND wary!
Don't think you can say they caused Michael to act toward Amber as he did, but they made it possible. Michael is the one to blame for his actions though.
I think even Michael thinks maybe he should have left with Joanna now. Nothing to say he has to, but I think his own guilt that he didn't, and how it will look for his reputation, is fueling his anger toward Amber.