The Choices You Make are Important ~ Social Skills and Conflict Resolution

You tell Anna that you saw Jen stealing her laptop and she is outraged. She confronts Jen and suddenly everyone is yelling and swearing at each other: Anna is yelling at Jen and Jen is yellng at you. You know you've done the right thing by telling Anna, but you've just broken up your trio of friends. (Well technically Jen did, but you told.)
What do you do?